276 



DK. A. E. TKUEMAJS" OX THE 



[vol. lxxiv 



moderately wide umbilicus, just becoming imparinode, anil show 

 the irregular cost* seen in JEgoceras dcedalicosta. 



Dimensions of W. D. L. Coll. No. 3861 :— 



Diameter. Whorl height. Whorl thickness. 



80 mm. 46 per cent. 57 per cent. 



47 44 51 



Umbilicus. 



25 per cent. 

 25 



These specimens are morphic equivalents of Androgynoceras 

 divaricosta, from which they differ in the greater symmetry 

 of the first lateral lobe (text-fig. (5, below) which resembles that of 

 2Egoceras latcecosta. 



iEGOCEKAS djedalicosta, sp. nov. (PL XXII, figs. 3 a & 3 b.) 

 Dimensions of holotype :— 



Diameter. Whorl height. Whorl thickness. Umbilicus. 



? 190 mm. 50 per cent. 47 per cent. 13 per cent. 



Whorl rounded, periphery arched, sides flattened, umbilicus small. 

 Ribs irregular, especially on the venter, where they occasionally 



Fig. 6.— Suture of iEgoceras sp., intermediate between M. latae- 

 costa and M. daedalicosta. (TV. D. Lang Coll. No. 3861.) 



57 mm. 



© 



o 



show small but distinct bends ; they divide sometimes on the lateral 

 area, and do not always unite with the outer tubercles. Tubercles 

 distinctly unpaired (about 7/4 on a quarter of a whorl). The 

 suture has the proportions characteristic of the genus ; the lobules 

 of the first lateral lobe are practically equal in length, a feature 

 shown by JEgoceras latcecosta. 



There" is very little trace of longitudinal striation on the outer 

 whorl ; at a diameter of 40 mm. the ornamentation is finer and 

 more regular, and striation is well-marked. 



The type-specimen was collected by Dr. Lang in the lied Band 

 (dcedalicosta sub-zone), St. Gabriel's Water, Dorset (No. 3862). ^ 



M. dcedalicosta differs from other species of Mgbceras in 

 having markedly unpaired tubercles and greater involution. The 

 young has fine paired tubercles until a diameter of 30 mm. 



