ZOOLOGICAL 



5* 



TROCHmai (Trochus, &c). Plate 28, Map iii. 



all 



The species of this family are about 300 in number, and are found in 

 seas, ranging from the arctic to the antarctic regions. Most of the 

 typical forms have a shell, which is remarkably like an inverted spinning- 

 top, and hence they are sometimes called "top-shells." About 16 species, 

 belonging to the typical genus Trochus, are found in British waters. 

 Margarita is an essentially northern genus, with about 20 species. A few 

 species of the family have been dredged at enormous depths. 



HALIOTID^l (Ormers). Plate 28, Map iv. 



The Haliotidae are interesting molluscs, found in all warm and temperate 

 seas. In Europe one species (Haliotis tuberculata) occurs as far north as 

 the Channel Islands, and on the strength of this it is claimed by some 

 conchologists as a British species. The 75 species of the family are all 

 placed in a single genus. The shells, on account of their beautiful pearly 

 lustre, are much used in inlaying, and hence have some commercial value. 

 In some countries these molluscs are used as food. 



PATELLID.E (Limpets). Plate 28, Map iv. 



This important family contains about 200 species, which are strictly 

 littoral in habit, occurring on rocks between tide-marks all the world over. 

 The single genus usually recognised {Patella) may be divided into numerous 

 sub-genera. Patella vulgata is an abundant and universal inhabitant of 

 the British shores, and furnishes in this and other countries an important 

 part of the diet of people living near the coast. 



OEDER POLYPLACOPHORA 



CHITONID.E (Chitons). Plate 28, Map iv. 



The Chitonidse are a group of molluscs of so remarkable a structure as 

 to form an Order to themselves. They possess a shell, which consists of a 

 series of eight separate pieces arranged in a row over the back, and are 

 thus, by their external appearance alone, easily recognised. About 300 

 species are known at the present day, and these occur principally in shallow 

 water in all parts of the globe. A few forms, however, have been dredged 

 from great depths, even from as much as 2300 fathoms. About a dozen 

 species claim a place on the British list. 



CLASS PELECYPODA 



OSTREIDJE (Oysters). Plate 28, Map iv. 



These are probably the best-known of all molluscs, since they furnish a 

 favourite part of the diet of almost all countries, and have been used from 

 the remotest periods of history. The artificial cultivation of Oysters is an 

 important industry in many countries, while their natural distribution is 

 practically cosmopolitan. About a hundred distinct species have been 

 described, which are all regarded as belonging to a single genus. Ostrea 

 edulis is the only representative of the family in British waters. 



PECTINID.S (Scallop-Shells). Plate 28, Map v. 



The members of this family are among the most beautiful of bivalved 

 molluscs, their shells being often prettily coloured and elegantly ribbed. 

 Over 200 species are known, most of which belong to the typical genus 

 (Pecten). Ten species are found in British seas ; the rest are found in all 

 parts of the world, and at various depths. 



AVIOULID^; (Pearl Oysters). Plate 28, Map v. 



From a purely monetary point of view this family of molluscs is the 

 most important of all, since certain of its species are the principal source of 

 the valuable concretions known as "pearls." The distribution of the true 

 Pearl-Oysters {Meleagrina) is shown separately on the map. From this it 

 will be seen that they occur off Madagascar, Ceylon, West Australia, Central 

 America, in the Red Sea and Persian Gulf, and in certain parts of Polynesia. 

 One of the most important pearl-fisheries is that of Ceylon, but fine specimens 

 are obtained in the Persian Gulf and other places. About 25 species are 

 known in the family as a whole, two of which (Avicula hirundo and Pinna 

 rudis) occur in British water. 



MYTILIDiE (Mussels). Plate 28, Map v. 



Of this family, which is of great importance from an economic point of 

 view, about 200 species are known, the great majority of which are marine 

 and found in all seas. The principal genera are Mytilus, with 70 species of 

 wide distribution but most abundant in the colder zones; Modiola, also with 

 about 70 species of universal distribution, and a few Asiatic forms living in 

 freshwater; Lithodomus, with 25 species, sometimes called "date-shells"; 

 Dreissensia, with about 20 species confined to rivers in various parts of the 

 Old World; and Mytilopsis, also a fresh- water genus, with a few species 

 found in a few small areas in the New World. A dozen species of Mytilidse 

 have a place on the British list. The most important of these is the common 

 Edible Mussel [Mytilus edulis), of which enormous quantities are used as food, 

 and also for bait, especially in deep-sea fishing. 



UNIONIDiE (Fresh-water Mussels). Plate 28, Map vi. 



The Fresh-water Mussels are found in ponds and streams in almost all 

 parts of the world, but they appear to be absent from Madagascar and 

 the Polynesian Islands. The family is an enormous one, more than 1200 



species having been described. Of these more than half are natives of the 

 rivers of the United States. The principal genera are Unio, of which three 

 species are found in Britain; and Anodonta, with two British species. 

 Unio margaritifer, occurring both in Europe and North America, produces 

 valuable pearls which, however, are not so fine in quality as those derived 

 from the Pearl Oysters (family Aviculidse). 



JETHERIHXa: (Fresh-water Oysters). Plate 28, Map vi. 



This family includes only a few species, placed in three genera, which 

 are confined to rivers and lakes in tropical Africa and the northern portion 

 of South America. The typical genus jEtheria contains all the African 

 forms (only four in number) ; Mulleria and Bartlettia are South American. 



CARDIID-E (Cockles). Plate 28, Map vi. 



About 150 species of this family are known, which live in shallow 

 water off the coasts of all parts of the world. Cardium is the principal 

 genus, with about 100 species, of which ten are found in British waters. 

 The Common Cockle (C. edule) is a familiar and widely-distributed edible 

 species. It ranges from Britain to the Baltic, and occurs also in the Black 

 and Caspian Seas. Adacna is a genus of special interest, inasmuch as its 

 eight known species are peculiar to the Caspian, Black, Azof and Aral 

 Seas. 



CYRENIDiE (Cyrena, &c.). Plate 28, Map vi. 



These molluscs inhabit fresh and brackish waters in nearly all parts of the 

 world. About 400 species are known at the present day, of which 100 are 

 placed in the typical genus Cyrena, 120 in Corbicula, 75 in Sphserium, and 

 60 in Pisidium. Britain possesses four species of Sphserium, three of which 

 are widely distributed in lakes, canals and ponds ; also five species of 

 Pisidium, which occur in slow-running or stagnant water in all parts of the 

 kingdom. 



CLASS INSECTA (Insects). 

 ORDER LEPIDOPTERA (Butterflies and Moths). 



SECTION RHOPALOCERA (Buttekflies). 



PAPILIONID^ (Swallow-Tails, &c). Plate 29, Maps i and ii. 



The Papilionidse (Map i) are a group of over 700 species, of world-wide 

 distribution (but absent from New Zealand), and containing some of the 

 handsomest known Butterflies. Some 14 genera are usually recognised, but 

 the majority of the species belong to the typical genus Papilio. The 

 geographical distribution of this genus corresponds roughly with that of the 

 family as a whole {see Map i). In the Neotropical Region, however, there 

 are probably as many species as in all the other regions put together. The 

 Common S wallow-Tail {P. machaon) is a native of Britain, occurring in the 

 fen districts of Norfolk and Cambridgeshire. 



The genus Omithoptera (Map i) comprises about 20 species of remark- 

 ably handsome appearance, some of them, indeed, being entitled to rank as 

 the finest of known Butterflies, and rivalled only by the magnificent 

 Morphos of the Neotropical Region. Omithoptera is an essentially Oriental 

 genus, but is represented also in North-eastern Australia and most of the 

 Papuan Islands. 



Thais (Map ii) is a genus peculiar to the Palsearctic Region. It com- 

 prises three species which occur in Southern Europe, Asia Minor and North 

 Africa, with a fourth doubtful form described some years ago from the 

 Amur Region. 



Parnassius (Map ii) is a group of about 30 species, with numerous 

 varieties, which are confined to the Palsearctic and Nearctic Regions. 

 Only four of these occur in the latter, and these are confined to the west 

 of the Rocky Mountains. 



Of other important genera in this family Druryia is confined to West 

 Africa, Teinopalpus to the Himalayas, and Eurycus to Australia. 



PIERID.E (Whites, Clouded Yellows, &c). Plate 29, Maps ii-v. 



This is an enormous family, comprising at least 1000 species, and occurring 

 in all parts of the world except New Zealand. The great majority of the 

 forms are of a prevailing white or yellow coloration, a feature which is 

 responsible for the popular names bestowed on them. Fully 50 genera are 

 differentiated for the reception of the various forms, or even more, according 

 to the views of various authors. 



Dismorphia (Map iii) is a Neotropical genus, containing over 80 species. 

 Many of these are remarkable from the fact that they mimic closely the 

 distasteful Butterflies of other families, such as Neotropida; and Acrseidai. 



Pieris (Map iii) contains about 200 species, which, according to some 

 authors, form a number of distinct genera. The distribution of the genus 

 (considered in the broad sense) is cosmopolitan, and four species occur in 

 Britain. 



Delias (Map iii) is a genus of often brilliantly-coloured Butterflies, 

 occurring in South-eastern Asia and the Australian Region. About 50 

 species have been described, eight of which are found on the Australian 

 Continent. 



The members of the genus Terias (Map iv) are small, mostly yellow 

 in coloration, and very difficult to distinguish from each other. About 

 150 species are known, which occur in nearly all tropical and subtropical 

 regions. Although ranging in Asia as far north as Japan, they do not 

 occur in North Africa, while in the New World two species occur even 

 northwards to New York. 



IMi 



