502 SMITHSONIAN MISCELLANEOUS COLLECTIONS [vol. 50 



In examining numerous specimens of Peracle reticulata Orbigny 

 and P. bispinosa Pelseneer, I find that, as Pelseneer suspected might 

 be the case, the thin layer comprising the reticulation, while not 

 exactly corresponding to the periostracum, is nevertheless dehiscent', 

 and we have several specimens of bispinosa which partially retain 

 it. The reticulation is sometimes partly hexagonal and partly quad- 

 rangular on the same specimen, and is more or less calcareous. 

 The puckered sutural margination, which was supposed to be char- 

 acteristic of P. bispinosa, often appears only late in life, the spine on 

 the lip only with complete maturity, so that it is probable that bi- 

 spinosa is only a completely developed mature phase of reticulata. 

 It is also likely that Limacina triacantha Fischer should be referred 

 to the genus Peracle, from which the shell seems to differ only by 

 its less elevated spire. 



Heterofusus peponum Gould is the fry of a Gastropod, probably 

 a species of Lampusia. This determination is made from Gould's 

 type. Limacina helicina Phipps, which is admirably figured by 

 Sars (Moll. Reg. Arct. Norveg., pi. 29), is instantly distinguishable 

 from L. pacifica Dall by its surface sculpture, which in the former 

 is uniform, close, and regular, while in the latter the axial striae are 

 sparse, distant, and irregular — in fact, nearly obsolete. Heterofusus 

 balca and retroversus may also be easily distinguished, as Sars' con- 

 trasting figures indicate. Clione dalli Krause, from Bering Strait, 

 is certainly an immature animal and probably, as believed by Pelse- 

 neer, the young of Clione limacina Phipps. Clione elegantissima 

 Dall, from the North Pacific, is, however, a much smaller and fully 

 mature animal, with no resemblance in form, color, or details of its 

 external structure to C. limacina at any stage of its development. 

 No one familiar with both in the living state could possibly con- 

 found the two species; but specimens preserved in spirits are subject 

 to such irregular contraction and modification that any one knowing 

 them only by such distorted material must necessarily be more or 

 less misled as to their natural appearance. 



