78 J. D. MACDONALD ON THE CLASSIFICATION OF THE GASTEROPODA. 



cpiaria ; but until something more is known of tlie anatomy of the latter, I cannot hazard 

 any further speculations on the subject of its natural position. 



It may now be asked, what is to be done with the FyrainidelliclcB, in which the lingual 

 memln'ane is quite unarmed and consequently can afford us no guide in classification. 

 The legitimate course in such a case as this Avould be to compare the whole tenor of the 

 anatomy with that of other families, whose position has been better determined. With 

 the hope of arriving at some successful result in this respect, I separately passed in review 

 the anatomy of Pyramiclella, Odostomia, and Eulinia, all of which genera are rightly 

 referred to the same family. But as tlie species of Fyrmnidella are usually more suited 

 for examination, their study has given me the chief grounds for the conclusion I have 

 formed, namely, that in their general anatomy they accord more closely with Solarium 

 and its allies than with any other family that I can suggest. Prom these, however, they 

 differ in two striking particulars, viz., the presence of minute otoliths in the ear-sacs 

 instead of otoconia, and the absence of dental organs both labial and lingual. In these 

 conditions, nevertheless, if my determination be correct, JPyramidella permanently repre- 

 sents the early state of Solarium. It is therefore not improbable that, if by any change 

 in the routine of nature dental organs were to make their appearance in Pyramidella, 

 they would assume the pavimental arrangement. Ho^n^ever this may be, there can be 

 little objection to the position chosen for the Pyramidellidce, immediately succeeding the 

 SolariidcB, while there is much to sustain it. 



The fore part of the head (or the muzzle) of Gasteropods presents at least three different 

 modifications which may be of service in classification. Thus, 1st, it may be simple, incapable 

 of retraction beyond what is distinguished as mere contractility ; 2ndly, proboscidiform 

 or retractile from the apex, invaginating itself mth one simple fold ; or, Srdly, it may be 

 a true proboscis, retractile from or near the base, with two resulting folds. The latter 

 form is present in all unisexual Gasteropods having a lingual ribbon with three rows of 

 teeth and under, and in some few families in which this organ presents seven rows. The 

 2nd occurs in the Oyprceidce ; and all the rest, with one or two questionable exceptions, 

 have simple muzzles with a dental armature of seven series and upwards. Pileo]^sis 

 IIv/)igaricus is figured and described as possessing a retractile proboscis of considerable 

 length; while the other members of Calyptrceidce have plain though more or less produced 

 muzzles ; and it is very doubtful whether the animal in question properly belongs to this 

 family, there being much in favour of its affinity to Vehitina, as suggested by Mr. Wood- 

 ward. I must say that I have never discovered a true proboscis in the animals of the 

 numerous Pileopsis-like shells which I have examined from time to time. The importance 

 of the distinctions here indicated is also exhibited in the case of the genus Urato, which 

 is admitted on all hands to belong to the Cyprceidce. 



Erato is anatomically related to Triton, or probably to Cassis, rather than to Cyprcea, 

 as the inspection of its labial and lingual dental organs will at any time prove. Its lengthy 

 proboscis is retractile from the base ; and the extremity of the tongue-sac can therefore 

 never lie freely in the visceral cavity — one of the most essential characters of the Cyprceidce, 

 though not peculiar to this family. 



The last case which I have to notice in this connection is that of Triforis. In a dextral 



