OASTROPOI'A l ." 1 "' 



..I1..I 



ilitr.i having lint> thread-like line- arranged in .1 reticulate, manner, while in 

 'In the surf, overeil !.\ >tn>ngly iinliricabing transverse lamella', the 



raised edges of \\lii.-h are serrat. i. 



('ems to us that f',./i/M. /,//,/ is in reality nearer Hucanin than Cyrtolitts. A 



ful comparison brings out what we conceive to be important agreement?. Thus, 

 in HuKinlii there i- a r.tther long apert ural slit, a large umbilicus and the whorls 

 increase somewhat slowly in si/e, while the surface sculpture, though differing in 

 It-tail, is of tlu> -aim- type. Of cour-e. we do not wish to be understood to say that 

 Bttcani'i aii-l < 'onrmlfHn are closely related, nor that there is any difficulty in keeping 

 the two genera -cparate. the strong dorsal keel, less depressed and more slowly 

 enlarging volutions, ami tin- <lirectness of the transverse imbrications in the latter 

 being very obvious peculiarities. Yet, when we consider the general sameness of 

 the types, we cannot escape the conviction that they were derived from the same 

 stock. The great development of the lamella-, each of which must at first have been 

 abrupt apcrt ur.il expansions, i< corroborative evidence for this view, since it is a 

 feature recurring in even greater development in TretininntHx, a genus that doubtless 

 WtOs derived from Xalpingoslomfi and Bucunin. 



In the new genus Ci/rtolitina (see pages 847, 856), the surface markings are some- 

 what .similar, but the lines of growth sweep backward on nearing the dorsum, causing 

 a sinus in the outer lip, the a pert ural slit is much shorter, and the volutions fewer in 

 number and much more rapidly enlarging. The long slit and the general form of 

 the shell of Conradella remind one greatly of the Devonian and Carboniferous genus 



'Ilia, Leveille, yet it is more than doubtful if there is any true relationship 

 lift ween them. In Porcellia the surface markings are of a different type, while the 

 innermost volutions are unsymmetrically coiled, showing that it was derived from 

 a pleurotomarid rather than a bellerophontid stock, the symmetric coiling of the 

 later whorls probably indicating partial atavism. 



Respecting the name of this genus, we would have been glad to restore Conrad's 

 riirar/inttlUfs (partitioned stone) were it not objectionable because it gives an 

 incorrect idea of the fossil. Conrad believed his P. compressus to be a chambered 

 shell. This, however, was soon learned to be an error, and as Hall placed the 

 species unreservedly into Ctjrtolites, which was proposed by Conrad at the same 

 time, all subsequent paleontologists have followed in ranking I'limi/molHm as a 

 synonym under Cyrlolites. Had the name ever attained currency, we would feel 

 ourselves bound to revive it, on the score of priority, despite its inappropriateness, 

 but as no one, so far as we can learn, ever adopted it, we thought it best to view the 

 name as one that has failed of being established because of incorrect and insufficient 

 definition. Yet we think it but justice to Mr. Conrad, who was a better paleontolo- 



