FROM THE UPPER CHALK. 



325 



Cardiaster pillula, Lamarck. PI. LXXI, figs. 1 — 3. 



Ananchytes pillula, 



Spatangus pkunella, 



Ananchytes pillula, 



nucleolites coravium, 

 Spatangus pillula, 



Ananchytes analis, 



holaster pillula, 



Ananchytes (Holaster) 

 Cardiaster pilula, 



Lamarck. Aniraaux Sans Verteb., torn, iii, p. 27, 



No. 11, 1816. 

 Mantell. Geology of Sussex, pi. xvii, figs. 22, 23, 



p. 193, 1822, 

 Deslongchamps. Encycloped. Method., torn, ii, p. 64, 



1824. 

 Cutullo. Saggio lie Zool., p. 226, pi. 2, fig. e, 1827. 

 Desmoulins. Etudes sur les Echinides, p. 406, 



No. 50, 1837. 

 Boemer. Norddeutsch Kreide, pi. 6, fig. 18, p. 3.5, 



1840. 

 Agassiz and Desor. Catal. raisonne, An. Sc. Nat., 

 torn, viii, p. 29, 1847. 

 PILULA, Forbes. Mem. Geol. Surv., decade iv, pi. viii, 1852. 

 (TOrbigny. Paleontol. Franqaise Terr. Cretaces, 

 torn, vi, p. 126, pi. 824, 1853. 



Diagnosis. — Test oblong, lofty, always more or less elevated ; sides tumid ; anterior 

 border round and flattened ; posterior accuminated and truncated ; base flatly convex 

 with sharp angulated sides, mouth near the anterior border ; vent elevated in the middle 

 of the posterior border ; upper surface highly arched, with a carina passing from the disc 

 to the vent ; apical disc narrow, elongated, and nearly central. 



Dimensions. 

 transverse diameter, 



The proportional dimensions of this Urchin vary considerably, a fact which may 

 best be illustrated by the measurement of six specimens of different bulk, in inches and 

 parts of an inch, as shown in the following table : 



-Height, ^ of an inch ; antero-posterior diameter, -^ of an inch 



20 



Yo of an inch. 



Height 



Antero-posterior diameter. 



Lateral diameter 



Vent above margin 



No. 1. 



No. 2. 



No. 3. 



No. 4. 



No. 5. 



No. 6. 



0-h 



Of 



H 



H 



OtV 



m 



1 



OA 



OtV 



Ot-V 



m 



m 



0^ 



OtV 



OtV 



OA 



OA 



OA 



Ot:\ 



OA 



Q-,% 



0^ 



t'A 



OtV 



Description. — Test oblong, always more or less elevated, tumid above, inflated at 

 the sides and flattened at the base ; the anterior border depressed, with the central 

 sulcus feebly developed and the posterior border accuminated and abruptly truncated. 



42 



