248 PNEUMONOBRANCHIATA. 



of the breathing cavity for a gill. The head is quite 

 destitute of the labial appendages noticed by Rang. 



Mr. Berkeley (and my own observations bear out 

 his accuracy) observes, that the animal is undoubt- 

 edly one of the Limnceidce, and nearly allied to 

 Physa. The pulmonary cavity, like that of Physa^ is 

 on the left side, with a valvular margin, in one corner 

 of which is situated the rectum ; between this and the 

 foot is the orifice of the matrix. They are herma- 

 phrodite, and may be observed in connection, as was 

 observed by Lister (Anim. Ang.}> about the end of 

 September ; and, as the latter author affirms, they fix 

 their spawn on stones in small gelatinous globules, 

 each containing many small eggs. (Pf e \ff er "> t. 161. 

 f. 21.) They have a retractile (and not exserted, as 

 described by Guilding) male organ at the base of the 

 left tentacle. 



These animals sometimes swim about on the sur- 

 face of the water, like Limncei, with the backs down- 

 wards. In fact they are Limncei^ with very short 

 conical, instead of long spiral bodies. 



Mr. Jeffreys doubts their being Pneumonobraneh- 

 ous, and Dr. Fleming, in one of his works, refers them 

 to the genus Crepidula ! and in his British Animals, to 

 the Pulmonifera. The tongue is a broad spiral band, 

 twisted at the end, longitudinally keeled, and set with 

 numerous close cross- bands of minute, close set, equal, 

 short triangular spines, directed backwards, and fur- 

 nished with a simple membranaceous margin on each 

 side, half as broad as the tongue itself ; the stomach 

 very much resembles the gizzard of a fowl, has a 

 strong muscular band on each side, and is nearly 

 filled with small flinty particles. 



