CIRRHOPODLS. 



385 



Our seas produce a small species (Patella anomala, 5Iull.). 



Tlie Discltiie, Larn., are Orbiculae whose inferior valve is notched with a fissure.* We must also approximate to 

 the Orbiculae, 



The Crania, Brug., whose animal has equally ciliated arms, but the shells have deep and round internal mus- 

 cular impressions, in which some have fancied they saw a likeness to the figure of a skull. One (A/iumia cranio- 

 laris, Linn.) is a native of our seas. There are muny fossil species, of which M. Hreninghaus has given a beautiful 

 monograph. 



[The Producta of Sowerby is a fossil genus, with a shell somewhat like a Cardium in figure, and rendered re- 

 markable by the manner in which the anterior margin is produced beyond the part inhabited by the animal. The 

 species are, to a certain extent, characteristic of the strata of secondary formation, and particularly of the carbon- 

 iferous or mountain limestone.] 



THE SIXTH CLASS OF THE MOLLUSCA. 



THE CIRRHOPODESt (Lepas and Triton, Linn.) 



In several points of view the Cirrhopodes effect a sort of connection between this sub- 

 kingdom and that of Articulated Animals. Enveloped in a cloak, and m a shell whose valves 

 often resemble those of several of the Acephales, their mouth is furnished with lateral jaws, 

 and the abdomen with filaments named cirri, arranged in pairs, composed of a number of little 

 ciliated articidations, and representing a kind of feet or swimmers, such as we see under the 

 tail of many Crustacea. The heart is situated in the dorsal region, and the branchiae on the 

 sides : the nei'vous system forms a series of ganglions in the abdomen. However, it may be 

 said that the cirrhous feet are merely the analogues of the articulated appendages of certain 

 Teredines, while the ganglions are in some respects only repetitions of the posterior ganglion 

 of the Bivalves. The position of these animals in the shell is such that the mouth is at the 

 bottom, and the cirri near the orilice. Between the two last cirri there is a long fleshy tube, 

 which has been sometimes inadvertently mistaken for a proboscis ; and at its base, near the 

 buck, is the vent. The stomach is puckered with a number of little cavities in its pai'ietes, 



which appear to fulfil the functions of a liver : 

 we notice besides a simple intestine, a double 

 ovary, and a double serpentine canal termi- 

 nacing in the extremity of the fleshy tube pre- 

 viously mentioned. The eggs pass through this tube, 

 and in their course are exposed to the influence of 

 tlie seminal fluid. The Cirrhopodes are all fixed. 

 Linnaeus considered them all as belonging to one 

 genus, which Bruguieres divided into two, and 

 these have recently been much subdivided. 



The Anatifa, Brug. — 

 lias a compressed cloak, open on one side, and sus- 

 pended to a fleshy tube, varying greatly as to tlie 

 number of testaceous pieces with which it is furnished. 

 The animal has twelve pairs of cirri, six on each side ; 

 those nearest the mouth are the shortest and thickest. 

 The branchiie are elongated pyraraidical appendages, 

 that adhere to the external base of the wliole of the 

 cirri, or of part of them. 



In the commonest species (Pentnlmmis, Leach) the two 

 principal valves have a considerable resenihlance to those of 

 a Mussel ; two others serve to complete a part of the margin 

 of the shell opposite the beak ; and a fifth odd one unites the 



Fiij. 131.— dronp ol Analifn, nttnt.'liccl to a shipi 



l" \Vo have ^llO 



1 tliat Lair 

 being act. 



