20 



Observations on the Terrestrial 



The strong resemblance between Conulus chersina and Conulus 

 fulva of Europe has been often remarked by American writers, 

 yet we are not aware that these species have ever been united by 

 any of them. The European writers Chemnitz, Pfeiffer, Reeve, 

 Forbes and Hanley unite the two. With the unaided eye it 

 would be difficult to point out the distinctions between the two 

 species which become apparent when magnified. Fig. 46 repre- 

 sents an enlarged view of Conulus chersina and Fig. 47 of Conulus 

 fulva. 



In C. chersina the shell is much more inflated, 

 the spire is more elevated, the whorls ai'e more 

 bulging, and the body whorl is not so angular 

 as in C. fulva ; the base also of C. chersina 

 is more convex than that of C. fulva, the form 

 Fig. 46. of the apertures of the two species are quite 



iinlike as will be seen by reference to the figures. In the specimens 

 of Conulus fulva which I examined there 

 appeared to be a minute umbilicus which is 

 wanting in C. chersina. The exterior surfaces 

 of the two species under a high magnifying 

 Fig. 47. power show marked difierences. Magnified 



four hundred diameters the incremental lines in C. fulva are seen 

 very strongly marked near the suture only ; in C. chersina these 

 lines are close set and equidistant ; in C. fulva they are finer and 

 are interspersed between larger waves of the periostraca, they are 

 slightly irregular also. In the same region in C. chersina we find 

 minute short longitudinal rugae which we failed to notice in C. 

 fulva. In the umbilical region in C. chersina the periostraca 

 appears to be waved, a similar structure is more conspicuous in 

 C. fulva. The chief peculiarity in C. chersina Avhich we have not 

 seen mentioned before in relation to this species, is the close set 

 revolving lines, {Plate 2, Fig. 4,) which are so delicate they can 

 hardly be discerned even when highly magnified. These lines 

 are more conspicuous in the umbilical region. I have found no 

 trace of this peculiar feature in C. fulva. 



Thomson, in the paper above referred to, gives the dentition of 

 Conulus fulva thus : 70 rows of plates, with 45 plates in a row, 



