Hyatt.] 



42 [Octobers 



one described by D'Orbigny ; or with any certainty, whether the first 

 variety is a distinct species, though it seems to be such. 



Androgynoceras appressum. 



And. appressum Hyatt, Bull. Mus. Comp. Zool., no. 5, p. 83. 



For perhaps the first four or five volutions the shell is similar to 

 the young of thinner varieties of M. laticosta. The extent of 

 envelopment, also, is slight ; soon however, on the last of the fifth or 

 first of the sixth the planicostan pilae split into several ridges united 

 at either end by tubercles. The abdomen at this period, the inclina- 

 tions of the sides, etc., closely resemble the characteristics of the 

 adult of the first variety of A . hybridum. 



LIPAiaOCERAS. 



Liparoceras indecisum. 



Lip. indecisum Hyatt, Bull. Mus. Comp. Zool., no. 5, p. 8. 



This is evidently a very much more accelerated form than even the 

 second variety of A. hybridum. It still preserves, however, the 

 form of the adult of this species. The young, if I am correct in 

 referring a young specimen from Bautenberg to this species, has plan- 

 icostan pilse certainly until after the completion of the fourth, and 

 probably until near the end of the fifth volution. 



Liparoceras Henleyi. 



Amm. Henleyi Sow., Min. Conch., vol. n, p. 161, pi. 172. 



Naut. striatus Rein, Naut. et argo., p. 85, pi. 8, figs. 65, 66. 



L. Henleyi Hyatt, Bull. Mus. Comp. Zool., no. 5. p. 84. 



This species differs from the last in not repeating the planicostan 

 abdomen at all, unless upon a volution preceding the last quarter of 

 the third. This seems improbable, though it may occur in some speci- 

 mens. At this period in the specimens examined all the adult char- 

 acteristics were well developed, and it only remained for them to 

 increase in size. The form of the shell is also precisely that of the 

 adult A. hybridum, second variety, or at least of that shell at 

 the end of the sixth volution. 



The L. Henleyi differs from L. Bechei in having larger and 

 more prominent tubercles, a broader whorl in proportion to the 

 height, and in the slighter involution of the young. For the first four 

 whorls the involution does not reach the internal line of tubercles, 

 leaving a larger umbilicus than in L. Bechei. In one specimen from 

 Lyme Regis the only distinction from Bechei consists in this single 



