MOLLUSC A. 451 



corneous jaw with a notch in the middle. The tongue is 

 merely armed with soft ti-ansverse ritlges, pointed before, 

 and terminated bv a short cartilaginous cone. There is a 

 sensible dilatation of the gullet, which marks the place of 

 the stomach, at the under extremity of which, is the rudi- 

 ment of a ca?cum at the pyloric opening. The intestine 

 makes several folds, chiefly in the liver, before it reaches 

 [he anus. The salivary glands reach to the extremity of 

 the gullet. The liver is divided into five lobes, wliich give 

 rise to two ducts that open into the pylorus. 



The circulating system consists of two vena? cava', which 

 give out numerous branches to the pulmonary cavity. The 

 aerated blood is conveyed by several ducts to a simple mem- 

 branaceous systemic auricle. Between the auricle and ven- 

 tricle there are two valves. The ventricle is more muscu- 

 lar than the auricle. The arteries, which take their rise 

 from a single aorta, are characterised by a peculiar opaci- 

 ty, and whiteness of colour, as if they were filled with milk. 



The organ of viscosity nearly encircles the pericardium. 

 It consists of regularly pectinated plates. Its excretory ca- 

 nal terminates at the pulmonary cavity. 



The organs of generation consist, in the female parts, of 

 an ovarium, oviduct, and uterus ; and in the male, of a tes- 

 ticle, vas deferens, and penis, together with the peduncu- 

 lated vesicle ; and, as common to both the sexual organs, 

 there is a cavity opening externally, in ^^hich, by separate 

 orifices, the uterus, penis, and vesicle, terminate. 



1. Extremity of the Tail Compound. 



12. Arion. — A mucous orifice at the termination of the 

 cloak. 



This genus has been recently instituted by M. le Baron 

 D'Audebard De Ferrussac, in his Histoire Nattirelle Gene- 

 rale et Partkuliere du Molhtsques Terrestres d Fluviatiles, 

 folio, Paris; 1819, 3e. liv. p. 53. The species of which it 



Ff 2 



