364 Mr. W. Clark on the Littorinide. 
of my position, that the spurious species belong to L. rudis, and 
of course follow the habitudes implanted by nature in the parent. 
It may be asked, does not the very important fact of the vivipa- 
rous reproduction of L. rudis and its varieties indicate something 
more than specific distinction? I partook of this opinion, but 
on consulting a naturalist of the highest authority, he informed 
me, that in the lower classes, the fact of an animal being vivipa- 
rous, without other circumstances, when its congener was ovo- 
viviparous, did not constitute sufficient grounds for generic di- 
stinction. The question is open, and I leave the solution of this 
problem to those who are better versed than myself in the my- 
sterious laws of nature which relate to the genesis of the Mol- 
lusca. 
I could adduce many more examples of various values, of the 
sad confusion that has crept mto and disfigured this highly in- 
teresting department of natural history, from the introduction of 
phantoms into our records, instead of soundly settled species. I 
refrain, and rest for the present on the great examples I have ad- 
duced in illustration of these observations, on the principle that 
“omne majus in se minus continet.” If the preceding remarks 
have the effect of causing greater circumspection in future in the 
creation of species, the object I have had in view will be accom- 
plished. 
I am, Gentlemen, your most obedient servant, 
WitiraM Crark. 
Postscript.—I take this opportunity to refer to some species 
of Mollusca which have lately been mentioned in our records. 
Having obtained fifty specimens of the Trochus pusillus of authors, 
I am enabled beyond doubt to state, that it is the living proto- 
type of the fossil Delphinula nitens of M. Philippi, tab. 25. fig. 4, 
and that the Skenea Cutleriana discovered by me is scarcely di- 
stinguishable from M. Philippi’s Delphinula elegantula, also a 
fossil, tab. 25. fig. 3; the only distinction 1s, that the spiral striz 
of Skenea Cutleriana are twice as numerous as those of D. ele- 
gantula ; this may arise from habitat, but I thmk the two distinct. 
The Trochus exilis of Philippi has not the slightest approach to 
S. Cutleriana. Whatever generic appellation may ultimately 
be applied to the Skenea divisa of authors, the same must be- 
long to the S. Cutleriana, as the character of the capillary striz 
is precisely similar. They are not Trochi, and I believe the 
Trochus pusillus is a Skenea; I shall however soon have an op- 
portunity of deciding, by seeing the animal. I am enabled to 
state that the Modiola phaseolina is a mere variety of Modiola 
modiolus, which when young, and indeed at all ages, varies both 
in shape and lustre.—I have fresh proofs of the fixity of the 
Foraminifera which shall appear shortly.—W. C. 
