iui i i:i:i:n i i \i. i 11 \i; \< it.i:i>i 



■It, though we failed in getting positive evidence of any- 

 thing more than a large Bolid keel. This, though distinct from the usual arietian 

 structure i>f this part, had not the black layer above the siphon which dis- 

 tinguishes the typical hollow keel oi some specii 



In the \\«'ll known >p- », the radical of 1 1 1 • ■ asteroceran w 

 the keel was broad and low with shallow channels, and the piloa were fold-like 

 with either -=inall tubercles or none, and the sutures in adults wen- lik<- those 

 1 The changes in • ■ rowth from the divergent-sided to 

 mvergent-sided whorl were rapid in Borne varieties, though in others the 

 l-abdomened and gibbous-sided whorl was retained even in adults. 1 In 7'nr- 

 nni. keel, deep channels, and quadragonal whorls were correlated with peculiarly 

 led and broadsides. Th< showed a tendency to specialization par- 

 allel with tli> E Coroniceras; nevertheless, in varieties of Tumeric and in the 



eding forms /.' and ( tfi, the differentials, with the exception ol the 

 ind sutures, tended to become extinct in consequence of the prepotent 

 influence of heredity in the transmission of geratologous characters. 



die! phenomena were also observed, as stated above, in individuals of 



• during old a_'e. when the adult differentials disappeared, and also 



in the adull of the progressive Coroniceran 



' , G ■. and trigonahtm, in which the quadragonal 



form, tubercles, etc. were similarly affected. 



In Oxyn . the differentials which enabled us to separate thi< from 



.1 rid ( H were tin- hollow keel and the sutures. The hollow 



appeared, as has been shown; in Oxyn. oxj/notum, hut it was filled with layers 

 of shell, though in other was really hollow, and appeared during the 



The increase of involution was correlative with the Bteadily 

 Ith and flatness of tin- sides, and an intensified trigonal outline. 

 / was moil- involute, more acute, and smoother even thai 



I lifferentiala of the Qreenoughi subseriea were less important chare 

 I ter form of whorl, which was more like that "i 



I fold-like piloa. These are less pronounced in the 1; 

 ' - ' in consequence of tie' prepoten 



.own in the more compressed, more involute, and 

 w borls. 

 'I'll. I. Si k hid. a- a rule, (shorter living chambers, usually 



one volution in length, and differed in tin- respect from the 

 branch of tin- I 



• should !»• noted here, thai m »/ the 



i 



i 



In I ficrentials, we mean only those which 



1 and contrasted in different imily, 



and which maj l»- 'i When a more 



i with an 



