with node-, <>r -welliii'j-. Margin of aperture simple or with 

 moxt IN formed of :i brOftd, Smooth ZOne ; a pert un- fre<pientl\ 



-iricted. r>ody-cliailll>er olie I e :ill(| :i < 1 1 l.'M'tr r whol'U 



Jon-. Aptvelm^ dixided. calcareous very thin. OOV6F0d with 

 lOleS oil the external -lirface. Lobes i|-u:ill\ deeply divided, 

 siphonal :MM| upper lateral lol.e usually of t he same length; ;i 

 stout :in\ili:iry sulnnil lolic ; lolmhir luxlics II.-UTUW. 



/v/.s- < livery -s IVoni ./v/orr/Y/x with ,S'/^,/,. ;///*.< iii 

 the middle Lias; aeeordiiii: in the snl.di vision into _irr(ii|is. it 

 emltraeo the Li.-issir riantilat a, Conmata and Uullata after the 

 ision of some heterogeneous elements; the last representa- 

 tives come from the Oxl'ordiaii (Steph. Collini, ()jij> , j//o/////x. 



Opp, 



l-'or thr ioiins \\itli contracted aperture, and constricted, 

 sonirtiines ireniculate body-chamber, the name Protophites, 

 Kl.rav, exists, thoiiuh it :ii>pi'ars to me that this separation is 

 not yet well enough established. 



Forty-one Jurassic species. 



i ATI M, Sowb. T. 102, figs. 540, 541. 

 s. BLAQDENI, Sowb. T. 102, figs. 550, 551. 



CJenus COSMOCERAS, WS..-I-I.M. 



Sijihonal side mostly with a smooth furrow; sculpture con- 

 sisting mostly of dividing ribs, directed forwards at the siphonal 

 side, frequently ornamented with nodes or swellings ; margin of 

 aperture in tin- young state frequently with ears, which are lost 

 by aue; body-chamber one-half whorl long. Lobes moderately 

 dividt-d; siphonal lobe distinctly shorter than the first lateral ; 

 id lateral repeating the form of the first; one or more aux- 

 iliaries. Aptychns apparently as in Stephanoceras. 



In respect to the limits of this genus, I differ very much from 

 those originally assigned it 1>\ Waairen, since I on one hand ex- 

 clude all the cretaceous forms except Cosm. verrucoxmit. and on 

 the other include the I'arkinsonia ; for the first change the 

 motive in;, v l, r to,md in //o/-///rx above; the last seems to me 

 nec(^>itate(l by this, that the whole ^eiius, in our present com- 

 prehension of it. is a complete >erie> of forms, which, with the 

 appearance of the siphonal furrow and development of the sculp- 

 ture, enters upon a line of variation divrrgini:- from 

 88 



