242 DR. J. D. MACDONALD ON THE 



dently occurred to me when studying the Helicinidse, and com- 

 paring them with the true Nerites, both aquatic and marine. I 

 would merely further take the liberty of inverting the order in 

 which Dr. Gray's families are arranged, as being thus disposed 

 more in accordance with the method adopted in classifying other 

 natural groups in the first part of this paper. This will be per- 

 mitted, I am sure, even by the most conservative, as by doing so no 

 natural affinities will be violated, while we shall have the satisfac- 

 tion of seeing that Selicina and its congeners are not thrown more 

 widely apart from the other so-called Pulmonifera operculata than 

 can possibly be helped. Eaphidoglossa (or needle-beset tongue, 

 as the word implies) is scarcely descriptive enough, or even 

 suggestive of the complex and beautiful structure which it is in- 

 tended to express ; but inasmuch as we have been now sufficiently 

 accustomed to associate the name with the thing signified, it 

 would be unnecessary to alter it. The term Heteroglossa may also 

 be retained as indicative of what may be clearly recognized to be 

 a morphological modification of the primary type (Eaphidoglossa). 



Dr. GTray saw the necessity of arranging Proserpina and Ceres 

 with the Scutibranchiata, their dentition being rapMdoglossal, 

 though it was only possible for him then to append them to what 

 had been already printed. He prepared the suborder Pseudo- 

 branchia for their reception. This was a step in the right direc- 

 tion ; and doubtless if he had not been misled by some means 

 so as to have supposed the dentition of Selicina to be septiserial 

 instead of rapMdoglossal, which it truly is, he would have placed 

 it in the same category with Proserpina and Ceres. There would 

 thus be good reason for removiDg both the Olygyradee* and Pro- 

 serpinidae from their association with the Cyclophoridse and Litto- 

 rinidEe. 



If we now take the two orders Heteroglossa and Eaphidoglossa, 

 and apply the test of analogy as suggested in the first part 

 of this paper, we shall find a rather interesting result. Thus 

 Cryptochiton in the former group would nearly represent the 

 shelless Deridobranchus in the latter ; Patella would be answer- 



* Olygyra, Say, is merely a synonym of Helicina, upon which Dr. Gray has 

 founded the family name Olygyradze, though the generic name of Helicina is 

 retained to the exclusion of Olygyra. In a somewhat similar way the family 

 name Olividce is preserved, while the generic name fStrrephcma is made to super- 

 sede that of Oliva. 



