74 CARBONIFEROUS CEPHALOPODA OF IRELAND. 



and there on the umbilical declivities. Lines of growth on the sides of the shell, 

 mostly too fine to be seen except with a lens, are more easily discernible on the 

 periphery, where they are crowded together, forming a deep, backwardly directed, 

 and sharply bent sinus; some very obscure longitudinal lines occur also here. 



Dimensions. 



Diameter of shell, rendered somewhat elliptic by pressure 



,, umbilicus (from edge to edge) 



5, ,, (from suture to suture) 



Height of outer whorl (dorso-ventral) 

 Width of periphery of outer whorl 

 Thickness of shell at umbilical edsre . 



o^ 



Large individual fioni llaUikeale. 

 (Science and Art Museum, Dublin.) 



■essure 73 



mm. 



. 46 



55 



. 35 



55 



. 18-5 



55 



. 8-5 



5' 



. 13 



55 



Bemarks. — M'Coy's description of the present species was drawn up from a 

 specimen half buried in the rock ; ^ it is contained in tlie Museum of Science and 

 Art, Dublin ("Griffith Collection"). He states that there are "very faint 

 traces of spiral strise on the inner or young volutions," but, with much more 

 perfect material than M'Coy had, I have failed to see any such ornamentation, 

 nor is it to be seen in the type specimen from which M'Coy's description was, 

 presumably, drawn up. 



Localities. — Clane, county of Kildare ; Argoul South and Cragard, county of 

 Limerick. 



Genus Dioeugoceeas, Hyatt, 1898. 



DiOEUGOCBEAS PLANJDOESATUM, /. E. Portloclc, Sp. 



1843. Naittilus planjioesatus, J. E. Porilock. Geology of Londonderry, 



p. 403, pi. XXXV, fig. 1. 



1893. DioBTiGOCZBAS PLAMBOESAiuar, A. Hyatt. Ciirboniferous Cephalopoda. 



Geological Survey of Texas, Fourth 

 Annual Report, 1892, p. 416. 



As will be seen from Portlock's description here given, this is a very pro- 

 blematical form, and the utility of dealing with it afresh is perhaps open to 

 question; were it not that Professor Hyatt has proposed a new genus for its 

 reception, I should probably have passed it by, as I have not access to the 

 specimen, and am not even aware of its present location. 



^ It is drawn on the plate free from the matrix; the forni and dimeii&iona of the specimen, 

 liowever, leave no doubt in my mind as to its reprtseutiug the .'■pecimen iu tlie " Griffith Collection." 



