ASSIMINEA. 97 



Palermo. He represents the tubercles as whitish, which 

 is not the case in O. Celticum ; otherwise his description 

 and figure suit our species. His specimens were only 

 3 millimetres long, and might have been immature. 



Family II. ASSIMINEID.E, (Assimmiidce) 

 H. & A. Adams. 



BODY spiral, enclosed in a turbinated shell : head furnished 

 with a broad snout : tentacles 2, cylindrical or club-shaped, 

 thick, and contractile : eyes placed at or near the tips of the 

 tentacles : foot oval : respiratory orifice on the right-hand or 

 outer side of the mouth of the shell. 



SHELL conical and strong : spire short : mouth roundish- 

 oval, more or less angulated or expanded at the base : pillar- 

 lip thick : inner lip united to the periphery, but not forming 

 a distinct peristome : outer lip sharp : operculum horny, pauci- 

 spiral ; nucleus on the inner side of the mouth. 



Genus ASSIMI'NEA*, Leach. PL IV. f. 1. 



As this appears to be the only representative of the 

 family (Paludinella of L. Pfeiffer and Optediceros of Dr. 

 Leith being mere synonyms) it would be superfluous to 

 repeat the description given above. 



The careful observations of Mr. Berkeley, in the 5th 

 volume of the ' Zoological Journal/ on the anatomy of 

 A. Gray ana, left very little doubt of this being a true 

 Pulmombranch. He could detect nothing like gills, 

 but found that " the vault of the cavity of respiration 

 was traversed by a multitude of minute vessels, all 

 tending one way towards a large vessel running down in 

 the direction of the heart ; which is exactly the struc- 

 ture in pulmoniferous Mollusca." Neither did Mr. 



* A ridiculous name. 

 VOL. V. F 



