84 CARBONIFEROUS CEPHALOPODA OF IRELAND. 



Dimensions. 



Specimen from Clane Large specimen from 

 of ordinary size. Enniskillen. 



Diameter of shell . . .93 mm. 190 mm. 



Height of outer wliorl . . . 33 ,, 66 ,, 



Diameter of penultimate whorl from suture 



to suture . . . . 35 ,, 95 „ 



Affinities. — Attention is drawn under the description of Vestinaidilus crateri- 

 formis to the resemblances between that species and the present one, which 

 therefore need not be here recapitulated. Another allied form is V. paucicarinatus, 

 the ventral and lateral ridges in which are a distinguishing mark separating it 

 readily from the present species, which except in the young shell (and according 

 to Hyatt ^ in the adolescent also) are not developed or very feebly so. Thei'e 

 is never any lateral or umbilical ridge or keel in V. cariniferus. 



Bemarks. — This species belongs to the group of crateriform and keeled shells 

 which Professor Hyatt has marked off from Cceloiiautilus and assigned to 

 de Ryckholt's genus VestinauUlus,~ a change which I have accepted. 



The present species appears to be one of the most abundant as well as wide- 

 spread in the Carboniferous limestone of Ireland. It seems to be much less 

 common in England. 



Localities. — Clane, county of Kildare; near Enniskillen, county of Fermanagh 

 (the largest specimen known) ; Little Island, near Cork ; Rathkeale and Ardtomiu, 

 county of Limerick. 



Vestixautilus cakinifekus, /. de C. Soiverby, sp. Var. magnicameratus, nov. 



Plate XXI, fig. 8. 



The presence of a species or variety closely allied to Vestinautilus cariniferus 

 has often suggested itself to me when looking over any large series of specimens 

 assumed to belong to this species. 



I have before me a specimen which, if the septa were not exposed to view, 

 might easily be mistaken for Sowerby's species ; their wide separation, however, 

 is a feature which cannot be overlooked, and one which entitles this form to at 

 least varietal rank. I therefore propose for it the name magnicameratus as 

 expressing its chief characteristic. 



' " Carboniferous Ceplialopods." Second paper. ' Geological Survey of Texas, Fourth Annual 

 Keport,' 1892, p. 420. 



- ' Notice sur les genres JS'autilus, Vestinautilus, &c.,' de Kyclibolt, 1852. 



