M L L U S C A. 



625 





8. ralagtm pi*ci**lif. This is the Turbo fontinalis 

 of British oonohologists, but th-st described by Muller 

 at Merita piscinalis. The whorls of the shell form in 

 this upeeies m short spire. It is very common, both 

 ! and Scotland. 



V . \j n DC Tit 1 ECTI NI3n A?f CHT A 



THIS order comprehends nearly all the animals with 

 spiral univalve shells which inhabit the sea, together 

 with a few which reside in fresh water. 



The foot is usually fortified above, on its posterior 

 extremity, with a corneous plate, which acts as a lid 

 to the shell, when the animal is withdrawn into the 

 cavity. The anterior extremity is in some of the spe- 

 cies doable. The anterior margin of the cloak forms 

 a thick band, or arch, rising from the foot, behind 

 which, is the portion of the body that is always con- 

 tained ia the shell, and which is covered with a very thin 

 Between the aaargin of the cloak and foot is situ- 

 ; the head, supyuatid an a short neck. The 

 are two in number, bearing eyes at their 

 or on short lateral processes which hare eons* < 

 to be considered as tentacula. The hood is frequently 

 emorginated, and sometimes fringed. The mouth is 

 more or ieas ia the farm of a proboscis, ia same cases 

 araaed within with apinous hps, or furnished wish a 

 loag issrvow spiral tongue, armed with spines, as in 

 the common periwinkle. The nature of this kind of 

 tengua, whose spiral extremity is free and lodged in 

 the abdomen, is not well understood. 



The entry to the gills is by large aperture between 

 the margin of the cUak and neck, at the middle, or 

 tawaide the right idc. These are contained in a cavity 

 ma the back of the animal, and consist of leaves ar- 

 ranged in one OT moat vows, which adhere to the walls 

 of the csrvity. At the entrance of this cavity is the 

 anus and oviduct. 



The male and female organs are considered not only 

 s distinct, bat as occarring on different individuals. 

 The evidence in support of this opinion is in many 

 cases complete. The pens* is in some external, and in- 

 capable of being withdrawn, while ia others it is re- 

 in a cavity in the right tenta- 



The body of the animal is attached to the shell by 

 ems of two twtarie*, which adhere to the pillar near 

 the same piace, and shift their position, by an arrange - 

 aaentiM* well nndnwtood, in proportion as the indi- 

 vidual iimsaiiii ia size. These masclea terminate in 



aMtfc 



Js of this order hare not been examined 

 in detail to admit of their distribution into 

 s, distinguished by characters founded on 

 erences of organisation. The form of 

 the shell has been resorted to, with the view of assist. 

 ing arrangement The characters thus furnished would 

 be useful and valuable, were they the index of any 

 fjoculiav internal structure. But, unfortunately, am. 

 atals, widely different in rtructure. inhabit shells of the 

 assne form, and rice versa, so that however useful the 

 mere conchologist may find the form of the shell to be 

 in his arrangements, it can only be regarded by the 

 at, occupying a subordinate place. Without 



the struc- 



ture of the few species which have been examined 

 anatomically, we shall merely point out the tribes and 



i ' ~_sV*_i. 1_ I I 1 1 1 



Jnneswnicn hare been contemplati-(l. and whose cha- 

 racters in a great measure depend on the chape of the 

 shell. 



VOL. XIV. PAHT It. 



The first TRIBE contains animals with spiral shells, 

 having an entire aperture. The anterior margin of the 

 cloak is likewise entire. It includes the greater part 

 of those shells included by Linnaeus in his genera Turbo 

 trochms and Nerita. 



The first FAMILY of this tribe, represented by the 

 genus Turbo, has the aperture of the shell nearly 

 round. All the species are furnished with an opercu- 

 lum. Some are known to be ovoviviparous, and it is 

 probable that all the species are so. Some have the 

 sexes distinct, in different individuals, as the Paludi- 

 na?, white in others the female organs only have been 

 detected. Some of the genera are marine, such as 

 Turbo, Delphinula, Vermicularia, Turritella, Scalaria, 

 OdiTstuniia, and Monodonta. The animals exhibit re- 

 markable differences in the form of the hood, the length 

 of the peduncles supporting the eyes, and the filaments 

 on the sides of the body. 



There is only one genus, the species of which reside in 

 fresh water, termed Paludina. It contains the Helix 

 vii-ifiara and tentaculata of British conchologists. Cu- 

 vier seems disposed to unite with this genus, the com- 

 mon asarine shell Turbo littoreus or Periwinkle. The 

 form of the foot and hood, however, are different, but 

 more especially Che tongue, which in the Paludina is a 

 fixed tubercle, while in the periwinkle it is strap-shap- 

 ed, free at one extremity, equal m length to the body, 

 and covered with spines. 



The second FAMILY is represented by the Linnean 

 genus Trochus. The aperture of the shell is somewhat 

 quadrangular. The foot of the animal is furnished 

 with an opercuhun, (unless in the genus Pyramidella, 

 in which it is supposed to be wanting,) and the body 

 sal each side is ornamented with filaments, usually three 

 in number, resembling t on t am la. All the species are 

 marine, and are included in the genera Trochus, Sola- 

 riiun, anil Pyraraidella. 



The third FAMILY, termed Conchylium by Cuvier, 

 is formed of shells having the aperture crescent-shaped, 

 as in the genus Helix, in which they were formerly 

 included. Two of the genera, Ainpullaria and Mela- 

 nia, are fiuviatile, residing in the countries near the 

 equator. The remaining genera, Phasianella and Jan- 

 thina, are marine. The Janthina vulgaris is destitute 

 of an operculum, but in its stead it is generally furnish- 

 ed with a cellular spongy body adhering to the foot, 

 which, in consequences of changes produced in its 

 density by unknown means, enables the animal to rise 

 to the surface of the water and float. When restrained, 

 it throws out a purple- fluid, like the Aplysia, lodged in 

 tl>e margin of the cloak, covering the gills. 



This species has been added to the British Fauna by 

 the late Miss Hutchins, who obtained many individuals 

 from a herd of them which came into Bantry Bay. 

 They have since been found on many other parti of the 

 Irish coast. 



We are disposed to place here, as a new genus, the 

 Jiulla veluiina of Muller, figured and described in the 

 Zoologin Danica,Tab. CI. fig. 1, 2, 3, 4. It is the Helix 

 faevigata of British writers. The foot is destitute of 

 lid or appendage, and is broad before and pointed be- 

 hind. The tentacula arc two in number, short and 

 filiform, with eyes at their external base. The head 

 i- l>r<md and short. In addition to these characters 

 given by Muller, we have been enabled to add the fol- 

 lowing, fiwoi a specimen, somewhat altered, which was 

 found in the stomach of a cod-fish. The animal ad- 

 heres to the shell by two linear muscles, one on each 

 side the cloak. The branchial cavity is towards the 

 left side. The tongue is spinous, narrow, with its free 



4 K 



