ZOOLOGICAL 



49 



CEPHALOCHORDATA. 



BRANCHIOSTOMATHLE (Lancelets). Plate 26, Map vi. 



The fish-like and primitive vertebrates known as Lancelets are of so 

 Peculiar a structure as to constitute a separate class to themselves of an 

 importance, from a morphological point of view, equal to that of the whole 

 of the fishes. They are marine animals, and the 16 known species are found 

 on the coasts of all parts of the world. Most of the records, however, are 

 tropical and subtropical, referring to localities between 40° N. and 40° S. 

 Branchiostoma lanceolatum has been recorded from many parts of the 

 British coast. 



CLASS MOLLUSCA (Molluscs). 

 ORDER CEPHALOPODA 



OCTOPODHXE (Octopus, &c). Plate 27, Map i. 



The Octopodidse occur off the coasts of nearly all temperate and tropical 

 regions. About 100 species have been described, and two at least occur 

 in British waters. They are solitary animals, inhabiting rocky shores 

 and the adults attain a huge size, some having been seen over 9 feet in 

 length. Their food consists principally of bivalved molluscs. In the South 

 of Europe they are sold as food, and are said to be excellent eating. 



ARGON AUTIDJE (the Paper-Nautili). Plate 27, Map i. 



The members of this family are all placed within a single genus 

 (Argonauta). They inhabit the warmer portions of all seas, and are reported 

 to be more active in the night. The shell of these creatures is a very 

 beautiful object, and was at one time supposed to be made by some other 

 mollusc, the Paper-Nautilus merely using it as a convenient dwelling-place. 

 It is now known, however, to be secreted by the animal itself. The male is 

 without a shell, and is a much smaller creature than the female. 



LOLIGINIDiE (Squids). Plate 27, Map i. 



The Squids or Calamaries, of which about 60 species are known, occur 

 in all seas. Three species are found in British seas, including the Common 

 Squid (Loligo vulgaris). The Cuttle-fishes of this family sometimes grow to 

 an enormous size. Specimens have been captured which, when measured, 

 were found to possess a body at least 7 feet long, with arms that stretched 

 a distance of from 24 to 30 feet. 



SEPIID.E (True Cuttle-Fishes). Plate 27, Map i. 



Over 30 species of this family are known, which are found in the seas 

 of all the world. They are, in general, much smaller than the members of 

 the preceding family, seldom exceeding a foot in length. Three species of 

 Sepia find a place on the British list, the best-known of which is usually 

 called the Common Cuttle-fish (S. officinalis). They are chiefly shore 

 animals, feeding on fish and crustaceans. In Italy they are much esteemed 

 as food. 



SPIRULID.E (Spirula). Plate 27, Map ii. 



Three species of this interesting family are known, all belonging to a 

 single genus (Spirula). The shells of these animals are well-known, since 

 they are washed ashore in all parts of the world. The living animal is, 

 however, very rarely seen, and very few good specimens have been obtained. 

 The best-known form is S. peronii, which is reported from British waters. 



NAUTILUS (Nautili). Plate 27, Map ii. 



The six living species of this family are confined to tropical seas, and 

 little is known of their habits. In many of the Polynesian Islands these 

 molluscs are used as food, while their elegant shells are in India made into 

 drinking-cups. The Nautili are the sole existing representatives of a 

 group which is known as Tetrabranchiate, and which includes many 

 thousands of species only known in a fossil state. The well-known 

 Ammonites of the fossil collector are referred by many authors to this 

 group. 



CLASS GASTROPODA. 

 ORDER PULMONATA. 



TESTACELLIDiE (Shelled Slugs). Plate 27, Map ii. 



This family of terrestrial molluscs possesses representatives in all the 

 zooo-eo°raphical regions, including two species which are on the British list, 

 though probably introduced. These belong to the typical genus (Testacella), 

 which contains besides a few species found in the South of Europe and 

 North Africa. Streptostylus is confined to tropical America, with about 50 

 species; Glandina, with about 150 species, is likewise chiefly American; 

 Gibbus, with over 40 species, is confined to Madagascar, Seychelles, and the 

 neighbouring islands ; while Paryphanta and Rhytida are confined to the 

 Australian region. 



LIMACID^I (True Slugs). Plate 27, Map ii. 



This is an extensive group, containing representatives in all parts of the 

 world. Some of the slugs belonging to this family are devoid of an external 

 shell possessing only a small internal plate ; others again possess a complete 



spiral shell within which the animal can wholly withdraw. The most im- 

 portant genera are Urocychis, confined to tropical Africa ; Parmarion, 

 which is entirely Oriental ; Helicarion, with about 100 species found 

 principally in the Oriental and Australian Regions ; Ariophanta, with over 

 500 species of universal distribution ; Parmacella, occurring chiefly in the 

 Mediterranean countries ; Limax, with over 1 00 species of world-wide 

 distribution ; Vitrina, with about 100 species inhabiting chiefly the 

 Northern Hemisphere ; and Zonites, confined to Europe and America. 

 The British forms of this family include nine species of Limax, one of 

 Vitrina, and eleven of Zonites. 



HELICID.E (Typical Land-Snails). Plate 27, Map iii. 



The typical Land-Snails occur in every part of the globe, and include 

 an enormous number of species. The slugs of the genus Arion are included 

 here, although sometimes placed in a separate family. Britain possesses 

 three species, with numerous varieties of this genus, which is characterised 

 by the absence of a shell. Curiously enough, these slugs, so abundant with 

 us, are unknown in America. The typical genus Helix is an enormous 

 one, with about 4000 species. Of universal distribution, this genus has 

 been divided into innumerable sub-genera. Britain claims at least 25 

 species, each of which has several named varieties. Lastly, Bulimus, with 

 over 300 species, is mainly South American. 



BULIMULID.E (Bulimulus, &c.). Plate 27, Map iii. 



This family, as at present constituted, is confined to the New World, 

 the Oriental Region, and the Australian Region. It contains several species 

 which were formerly placed in the genus Bulimus (Helicidse), but which, 

 owing to certain characters formerly overlooked, are more properly removed 

 from that position. The great majority of the members of the family belong 

 to the typical genus Bulimulus. 



UROCOPTnLE (Urocoptis, &c). Plate 27, Map iii. 



This family, formerly bearing the name Cylindrellidse, is entirely con- 

 fined to tropical America. Their shells are very long, with many whorls, 

 and often beautifully sculptured. About 250 species have been described, 

 Urocoptis (or Cylindrella) containing about 200, and Macroceramus most of 

 the remainder. 



PUPID^I (Pupa, &c). Plate 27, Map iii. 



This group is a very extensive and somewhat heterogeneous one, con- 

 taining representatives in all parts of the world. The typical genus, Pupa, 

 contains about 400 species found universally, but more characteristic of 

 temperate regions. Several species occur in Britain. Vertigo has an 

 equally extensive distribution, with about 100 species; while Clausilia 

 contains at least 700 species, which are mainly inhabitants of Europe and 

 Asia, with five in Britain. Of other genera, Anostoma, Odontostomus, 

 Megaspira and Strophia are American; Bidiminus belongs to the Old 

 World; Balea is European; while Godiaxis is confined to the Solomon 

 Islands and Australia. 



STENOGYRID^ (Agate- Snails, &c). Plate 27, Map iv. 



Over 500 species of this family are known, and these have a world-wide 

 distribution. The genus Achatina is probably the most important, contain- 

 ing about 80 species, which are confined to the Ethiopian region, and 

 known as Agate-Snails. Their shells are handsomely marked, and 

 among them are the largest land-shells known. Stenogyra, the typical 

 genus, contains 250 species of universal distribution; while Ferussacia is 

 an interesting genus, confined principally to the Mediterranean region, the 

 Canary Islands, Madeira, and the Malay Archipelago. 



SUCOINEID^ (Amber-Snails, &c). Plate 27, Map iv. 



The Succineidse are found all over the world, and contain over 200 

 species, the great majority of which constitute the typical genus, Succinea. 

 Half a dozen species of this genus occur in Britain. The molluscs of this family 

 may be called subaquatic, since they live in damp places, on aquatic plants, 

 or in marshes. The genus Romalonyx, with about half a dozen species, is 

 confined to the West Indies and Brazil ; while Hyalimax has a still more 

 limited distribution, occurring only in Mauritius and the Nicobar Islands. 



LIMN^ID^E (Fresh-water Limpets, &c). Plate 27, Map iv. 



The molluscs of this family are inhabitants of fresh-water, but at the 

 same time are air-breathers, and hence come to the surface at intervals to 

 renew their supply of free oxygen. The family, as a whole, has a universal 

 distribution, as have also the principal genera Ancylus (Fresh-water 

 Limpets), Planorbis and Limnsea (Pond-Snails). Of these three o- e nera 

 Britain possesses two, twelve, and eight species respectively. Gundlachia 

 (five species) is found in the United States, Cuba, and Tasmania; Latia 

 (two species) is confined to New Zealand ; Pompholyx is Californian ; while 

 Ghoanomphalus is only found in Lake Baikal, occurring in that lake at a 

 depth of over 1000 feet. 



PHYSID.E (Physa, &c). Plate 27, Map iv. 



Although a comparatively small group, the Pond-Snails of this family 

 have an almost universal distribution. The two principal genera are Physa, 

 with about 100 species, and Aplecta, with about 25. In Britain the two 

 species, Physa fontinalis and Aplecta hypnorum, alone represent the family, 

 the latter being abundant and widely distributed in slow rivers, canals and 

 ditches. 



