78 J. D. MACDONALD ON THE CLASSIFICATION OF THE GASTEROPODA. 
quaria ; but until something more is known of the 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 Pyramid ellidte, in which the lingual 
membrane is quite unarmed and consequently can afford us no guide in classification. 
The legitimate course in such a case as this would 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 Pyramidella, Odostomia, and Eulima, all of which genera are rightly 
referred to the same family. But as the species of Pyramidella 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, Pyramidella 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. However this may be, there can be 
little objection to the position chosen for the Pyramidellida?, immediately succeeding the 
Solo Hides, 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 with one simple fold ; or, 3rdly, 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 Cypraidce ; and all the rest, with one or two questionable exceptions, 
3 simple muzzles with a dental armature of seven series and upwards. Pileopsis 
Rungaricus 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 Velutina, as suggested by Mr. Wood- 
ward. I must say that I have never discovered a true proboscis in the animals of the 
numerous Pileopsis-\i\Q 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 Erato, which 
is admitted on all hands to belong to the Cypr widce. 
Erato is anatomically related to Triton, or probably to Cassis, rather than to Cypr<ea> 
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 Cyprceida, 
though not peculiar to this family. 
The last case which I have to notice in this connection is that of Triforis. In a dextral 
hav 
