316 



CONCHOLOGY. 



lished memoirs and treatises on conchology, and 

 many interesting facts had been collected, shedding 

 much additionallight on the science. Part of tiie 5th 

 ami the \> hole of the 6tli and 7th volumes of the His- 

 toire naturelle des Animaux sans P'ertebres, are devot- 

 ed to the conchyliophorous animals, the proper subjects 

 of conchology. In this excellent work, Lamarck has 

 Improved upon the views of his friend Bruguiere in the 

 following particulars : not confining himself to the 

 consideration of the shell; viewing the shell as for- 

 ming part of an animal ; introducing into concho- 

 logy a great number of new generic groups ; using a 

 very rigorous and exact terminology ; and treating 

 as tin- foundation of the principal division among bi- 

 valves, the number of the muscular impressions. 

 He has also abandoned the divisions, imiltivalvcs, 

 bivalves, and univalves, which had been followed by 

 most of the preceding conchologists, and has in- 

 creased the number ot genera to 261, to which we 

 have added 20, marked by an *, and given brief ge- 

 neric characters of the whole. The specific descrip- 

 tions of Lamarck, although short, are admirable for 

 their precision, and the skill displayed in them in dis- 

 tinguishing clearly minute specific differences. The 

 study of them will be found, by young naturalists, 

 very beneficial and instructive. 



In 1812, H. M. Ducrotay de Blainville read, be- 

 fore the philomathean society, a memoir, pointing 

 out a necessary relation subsisting between the shell 

 and the respiratory organs, and drawing therefrom a 

 new principle of arrangement, depending on the ex- 

 istence or non-existence of a symmetry or regularity 

 of form in those organs, and the protecting body, the 

 shell. 



In 1825, De Blainville published his Manuel de 

 Malacologie et de Conchyliologie a very valuable 

 work, to which we are indebted for most of the his- 

 torical facts recorded in this article. The first chap- 

 ter of the second section of this work, consisting 1 of 

 eighty pages, treats of shells, or the principles of con- 

 chology, and recommends itself strongly to students 

 by the fulness, accuracy, and clearness of its defini- 

 tions, and the consistency of its general views. 



In modern times, the study of the mollusca and their 

 coverings lias become very important from geological 

 considerations. As particular genera are known to 

 belong to particular strata of the earth's crust, and 

 as the positions assumed by the living animals are 

 known, the ascertained position of the fossils deter- 

 mines, with sufficient certainty, whether the stratum 

 has undergone removal, disruption, or subversion since 

 the death of the animals. The most interesting con- 

 siderations are presented to the inquiring mind by 

 some of the genera of microscopic shells ; and the 

 magnitude of the results produced by their infinite 

 multiplicity causes their importance in the economy of 

 nature to be felt with astonishment and admiration. 

 Take, for instance, the miliolites, thus commented on 

 by Lamarck : " The miliolites is a shell of most sin- 

 gular form, and perhaps one of the most interesting 

 to study, on account of its multiplicity, in nature, and 

 the influence which it lias upon the condition and 

 size of the masses at the surface of the earth, or which 

 compose its external crust. It is one of those numer- 

 ous examples which prove, that, in producing living 

 bodies, what nature seems to lose in size, she fully 

 regains in the number of individuals, which she mul- 

 tiplies to infinity, and with a readiness almost mira- 

 culous. The bodies of these minute animals exert 

 more influence on the condition of the masses com- 

 posing the earth's surface, than those of the lar- 

 gest animals, such as elephants, hippopotami, whales, 

 &c., which, although constituting much larger in- 

 dividual masses, are infinitely less multiplied in 

 nature. In the environs of Paris, some species 



of miliolites are so numerous, tliat they fonn almost 

 the principal part of the stony masses of certain 

 ranges." The naturalists of America have also con- 

 tributed much valuable matter to the science in ques- 

 tion, and some new genera and many new species 

 have been added by their labours. Among the scien- 

 tific gentlemen in America who have written on this 

 subject, are Thomas Say, of Philadelphia, the late 

 D. H. Barnes, of New York, doctor Hildreth, doctor 

 Jacob Green, and Isaac Lea, of Philadelphia. In 

 Britain, Drs Leach, Turton, and Fleming, Messrs 

 Sowerby and Swainson, General Bingliam and Cap- 

 tain Brown, liave added many new genera and spe- 

 cies of existing shells ; and Sowerby^ work on fossil 

 shells will be a lasting memorial of his skill and re- 

 search. 



Sj/noplical Table of tlie Generic characters of Lamarck\ 

 Conchological Si/stetn ,- arranged according to the des- 

 cending scale; with some additional genera. 



CLASS I. MOLLUSCA UNIVALVES. 



ORDER I. HETEROPODA. 



Having a head; two eyes; no arms; body free; swims hn. 

 montnlly ; destitute of afoot; fins, but irregular. 

 Phytliroe and Pterotrachea, destitute of shells. 

 Curnaria, Cymbium, pL 17, tig. 1. Coiiica), compressed, uni- 

 locular, convoluted ; some are keeled ; aperture obloug. 



ORDER II CEPHALOPODA. 

 DIVISION I. CEPHALOPODA SEPIARIA. 



FAMILY I AMMONACEA. 



Mantle bag-shaped ; head protruding from the bag, with in- 

 articulate arms, having suckers around the mouths ; two eyes; 

 mouth with horny mandibles. 



The genera are Sepia, Lotigo, Loligoprii, and Octopus, all 

 destitute of shells. 



DIVISION II. CEPHALOPODA MONOTHALAMA. 

 Argonauta Argo, pi. 17. fig. 2. Unilocular, involute ; keel 

 double and tuberculated. 



DIVISION III. CEPHALOPODA POLYTHALAMA. 



FAMILY 1. AMMOXACEA. 



Baculites, Turrilitet, Ammonocerai, Orbulitet, and. Ammoni- 

 tet, are fossil. 



FAMILY II. NAUTILACEA. 



Nautilui pompiliut, pi. 17, fig. 3. Multilocular, volutions 

 concealed ; septa perforating the disk. 



Numtnulites, yorticiiilis, Po/ystomella, Siderolitet, and Dn- 

 corbis, are fossil. 



FAMILY III. RADIOLACEA. 

 Placentula, Lenticulina, and Rotaliii, fossil. 

 FAMILY IV. SPHEHULACEA. 



Melonia, fossil. 



Miliola concentrica, cells transverse, surrounding the axic, 

 aperture at base of last volution. 



FAMILY V. OHISTACKA. 



Orbiculina, Crittellarea, and Renulina, principally fosbil. 

 FAVILY VI. LITUDI.ACEA. 



Lituo/a and Spirolina, fossil. 



Spirula Peronii, pi. 17, fig. 4. Multilociilu, cylindrical, re- 

 rolving on the apex; partitions equi-distaut, with a communi- 

 cating syphon; aperture round. 



FAMILY VII. OBTHOCBRATA. 



Conilitei and Hippuritet, fossil. 



Nodotaria radicuta, pi. 17, f. 5, straight, or slightly bent, 

 nodose ; septa perforated. 



Orthocera raphama, straight, or slightly bent ; grooved 

 longitudinally; coils divided by septa, perforated by a tube. 



Selemnitet, fossil. 



ORDER III. TBACBELIPODA. 



SECTION I. ZOOPBAQUCS TUACHELIPODA. 



Body of animal spirally convolute posteriorly, separated 

 from the foot ; shell spiral, enveloping the animal. This order 

 is divided into three section*. 



FAMILY I. INVOLUTA. 



Conut betulima, pi. 17, f. 6. Turbinate, convolute, aper- 

 ture longitudinal, effuse. 



Oliea utricultu, pi. 17, f. 7. Subcylindrica', spire short, with 

 channelled sutures: columella obliquely plaitrd. 



Anr.illaiia glandiform**, pi. 17, f. 8. Subcyiindrical, spire 

 short} aperture hardly eroarginate at the base; columella, with 

 a vanx at its base. 



Terebellum tabulation, pi. 17, f. 9. Subcyiindrical, apex 

 sharp, aperture narrow, notched at base, columelln smooth. 



Cypreea lynx, oblong, margins involute; aperture dentate 

 on each side, pi. 17, f. 10. spire nearly imperceptible. 



Orvla nfrrucoia, pi. 17, f. 11. Turgid, margins convolute, 

 the left one toothless; aperture longitudinal, extremities 

 effuse. 



