617 



MALACOLOGY. 



MALACOLOGY. 



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one to most. To the bulk of the Bivalves, or Conchas, a Tethys is 

 assigned as the animal; to the bulk of the Univalves with a regular 

 spire, a Limax or Slug, which last is stated to be the animal of Pinna 

 among the Bivalves ; and yet the wonder is how Linnseus approached 

 so nearly to a natural arrangement with the scanty materials for 

 scanty they were when compared with the information that we now 

 possess which formed the groundwork of his classification. Upon 

 this system almost all scientific collections of shells were arranged 

 till within these few years ; and so bigoted were many of the followers 

 of this great man, who would have been the first to remodel his 

 arrangement as new light poured in upon him, that every attempt at 

 adopting the views of Cuvier, Lamarck, and others, and even those 

 of Bruguiere, founded upon the structure of the animals, was for a 

 long time resisted, and almost resented as a presumptuous attempt at 

 ' genus-making.' 



Daubenton had read to the Academy of Sciences at Paris a memoir 

 on the systematic distribution of shells, in which, whilst he admitted 

 that an acquaintance with these alone might suffice for arrangement, 

 he remarked that a knowledge of the animals, or soft parts, was 

 indispensable for forming a complete system of conchology and a 

 natural distribution of these exuviae. But though this indefatigable 

 anatomist broached this opinion, he does not appear to have carried 

 his plan into execution. 



Guettard seems to have been the first who carried out the suggestion 

 of Daubenton; for in 1756 he read a memoir inserted in the ' Trans- 

 actions' of the same academy, and therein established upon sound 

 principles the necessity, in forming a classification of shells, of haviug 

 recourse to the animals, or soft parts which they inclose, and a part 

 of which the shells are. He did more; for he well characterised, 

 upon the principle advocated by him, several genera, especially among 

 the Univalves, as they were then called. And although he acknow- 

 ledges that his information with regard to the Bivalves was not 

 sufficient to enable him to carry out his views in the same manner 

 with regard to them, he observes that they must be susceptible of 

 being characterised with reference to the animals, or soft parts, as 

 well as the Bivalves. Guettard further pointed out the division of 

 shells into Terrestrial, Fluviatile, and Marine, and paid particular 

 attention to the presence or absence of the operculum. There can be 

 little doubt that these observations determined D'Argenville to add 

 to his second edition of ' Conchy liologie ' (1757) a number of figures 

 of the animals, or soft parts, under the name of Zoomorphoses : these, 

 it is true, are many, if not all of them, very bad. 



The principles of Guettard were in the same year (1757) more 

 extensively applied by Adanson in his ' Histoire Naturelle du Senegal 

 Coquillages.' He distinguishes all the external parts of the animals 

 and the shells. In the Univalve shells, as they were then called, or, 

 as Adanson denominates them, the Lima^ous, he points out the whorls 

 (spires), the apex (sommet), the aperture, the operculum, &c. ; and 

 in the Bivalves, under the name of Conques, he treates of the valves, 

 which he terms battans, and notices their equality or inequality 

 whether they shut close or gape at any point the hinge, and the 

 number and form of the teeth composing it, with the cavities which 

 they form the ligament, considering it as to form and situation the 

 muscles, or rather muscular impressions, with regard to their figure, 

 size, and number ; the nacre, &c. Out of the modifications of these 

 parts of the bivalve shell he forms divisions as five depending on the 

 variations of the hinge ; three depending upon the relative situations 

 of the ligament externally, internally, &c. ; three depending upon the 

 modifications of muscular attachment, namely, 1 at, Couques with one 

 muscular attachment; 2nd, Conques with two muscular attachments; 

 and, 3rd, Conques with three muscular attachments ; and three depend- 

 ing upon the presence or absence of the nacre and its modifications. 



In the animals, or soft parts, of the Limaeons, he directs his 

 attention to five principal parts : 



1. The Tentacula, or tentacles, which he names horns (cornes), and 

 which he considers with regard to their number and shape as fur- 

 nishing specific character, according as they are absent, or as there 

 are two or four, or according to their conical or cylindrical form, the 

 absence or presence of convexity (renflement) at their origin, and 

 their situation at the root, or at the extremity of the head. 



2. The Eyes their absence or presence; and in the latter case, their 

 situation upon the head at the internal side of the root of the tentacles, 

 behind the tentacles, towards their internal side, at the origin of the 

 tentacles on their external side, above the root of the tentacles on 

 their external side, at the middle of the tentacles on their external 

 side, and at the summit of the tentacles. 



3. The Mouth, as provided with two jaws without a proboscis, or 

 with a proboscis without jaws. 



4. The Trachea, or respiratory orifice, as formed by a simple hole 

 situated on one of the sides of the animal, or by a long pipe which 

 has its exit near the back. 



5. The Foot, according as it is divided by a transverse furrow at its 

 anterior part, or not. 



The Conques are regarded by Adanson with reference to four 

 principal parts, namely : 



1. The Mantle, which may be cither divided all round into two 

 lobes, or divided on one side only, or form a sac, open only at the 

 two opposite extremities. 



2. The Trachea, or tube, which may be either single, and in the 

 form of an aperture, double in the form of apertures, double in the 

 form of separate and distinct pipes, or double in the form of united 

 pipes. 



3. The Foot null, or not appearing externally, or appearing 

 externally. 



4. The Byssus, or Threads, which exist in some species, and do not 

 exist in others. 



The shells which he had observed at Senegal are figured and 

 distributed generally in the following order, under two families : 



Family I. LIMAQONS. 

 Section 1. Lima9ons Univalves. 



Genera: Cymbium. Sulinus (Physa of the moderns). Corelus 

 (Planorbis of Guettard).- Pedipes (Auricula of Lamarck). Cochlea 

 (Bulimui of Bruguiere). Lepas (Patella of modem authors, and also 

 embracing the Chitons). Haliotis. Yetus (Valuta of Lamarck, 

 Cymba of Broderip). Terebra. Porcdlana (Marginella and Oliva of 

 authors). Cypraa. Peribolus (young of Cypnea and small Margl- 

 nellw). 



Section 2. Limacons Operculiis. 



Genera : Strombus (Conus of the moderns). Purpura (including, 

 with the true Purpurce, Dolium, Cassidaria, Murex, Strombui of the 

 moderns, some Mitral, &c.). Buccinum. Centhium. Yermetut. 

 Trochus. Turbo. Natica. Nerita,. 



Family II. CONQUES. 

 Section 1. Couques Bivalves. 



Genera : Ostreum (Ostrea of the moderns). Jataronus (Spondy- 

 lus (?) of the moderns). Perna (including Mytilus, Modiola, Avicula, 

 Pinna, and Cardita}. Chama (including Venus, Cytherea, Mactra, 

 Cardita, and some of Solen; but apparently none of the Ohamce of 

 modern authors). Tellina (Donax of the moderns). Pectunculus 

 (including Cardium, Area, and some true Pecttmculi of Lamarck). 

 Solen. 



Section 2. Conques Multivalves. 



Genera : Pliolas. Teredo. 



Such is the system of Adanson ; and although it presents errors, 

 which would very probably have been avoided by so good an observer 

 if he had lived at a later period, when this branch of knowledge 

 became better known, we must allow him the merit of being the first 

 who practically applied the principle of classification based on the 

 structure of the soft as well as the hard parts, or, in other words, on 

 the organisation of the animal and shell. 



Geoffroy, a physician of Paris, applied the same principle in his 

 little ' Treatise on the Terrestrial and Fluviatile Shells ' in the neigh- 

 bourhood of that city. His genera of Univalves amount to five only, 

 namely, Ancylus, Cochlea, Succinum, Planorbis, and Nerita. His 

 genera of Bivalves consist of two, Chama and Mytilus, in the first 

 of which he places Oyclas, and in the second an Anodon and a Una. 



Miiller, the Dane, presented zoologists with a system founded on 

 the same principle, which, whilst it was more complete than that of 

 Guettard, inasmuch as it extended to all couchiliferous animals, was 

 less natural than that of Adanson, and altogether inferior to it, as far 

 as Adansou's went ; but it was much more elaborate, and demands a 

 great share of praise. The author of the ' Zoologia Danica,' in his 

 ' Vermi'im Terrestrium et Fluviatilium Historia," adopts three primary 

 divisions Univalves, Bivalves, and Multivalves. 



He divides the Univalves into three sections : 



1. Those Testaceous Univalves whose shell is pierced through and 

 through ; and in this section he places the Echini and Dentalium. 



2. Those which have a very large aperture, consisting of Akera 

 (Sulla of modern zoologists), Argonauta, Sulla (Physa of Draparnaud 

 and others), Succinum (Limnma of the moderns), Carychium, Vertigo, 

 Turbo, Helix, Planorbii, Ancylus, Patella, and Haliotis. 



3. Operculated Testaceous Univalves, in which he places the genera 

 Tritonium (Succinum of Linnwus), Trochus, Nerita, Valvata, and 

 Serpula. 



The Bivalves are divided by the same author into two sections 

 only : the first consisting of those which have a toothed hinge, including 

 Terebratttla, a new genus; the second, of those which have a toothless 

 hinge, including two new genera, Anomia, and Pecten, which he sepa- 

 rates from the Oysters. 



The Multivalves comprise the genera Chiton, Lepaa, and Pholas. 



There can be little doubt that it was to these authors (among whom 

 we do not include Muller, whose works appeared subsequently, nor 

 Geoffroy, whose treatise appeared nearly simultaneously) we owe the 

 amended arrangement of Linnseus as it finally appeared in his last 

 edition of the ' Systema Natura)' (the 12th, 1767), and as we have given 

 it above. In the earlier editions the term Mollusca does not seem to have 

 occurred to him. The Naked Molluscs are distributed among the order 

 Zoophytes, of his class Vermes, and the Testaceous Molluscs formed 

 his third order of that class, Testacea. Among the first we find 

 Tethys, under which he arranged the Holothuria ; and Limax and 

 Sepia, which he placed near the Hydra. The second were not yet 



