AKT. 10 CRETACEOUS FAUNAS OF THE CAEOLIN"AS STEPHENSON 5 



Wieser, chief scientific illustrator of the Geological Survey, who also 

 made the several drawings. 



DESCRIPTION OF SPECIES 

 CASSIDULUS KELLUMI, new species 



Plates 1, 2 ; plate 3, figs. 1, 2 



Description. — Test broadly ovate in basal outline, rather high and 

 dome-shaped; base slightly concave, with two broadly expanding 

 concave areas extending from the peristome to the ambitus, one on 

 either side of the posterior center ; these concave areas are separated 

 from each other by a broad, low, rounded posterior ridge which ends 

 at the ambitus in a slight protuberance or angulation below the 

 periproct ; a slight protuberance on the ambitus also marks the outer 

 corners of each of the two concave areas at equal distances from the 

 separating ridge and each protuberance is continued as a faint ridge 

 up over the test; the protuberances and concave areas produce a 

 slightly truncated effect on the ambitus at either side of the posterior 

 center. The upper surface is not smoothly domed, for each am- 

 bulacral area is distinctly raised between the pore bands, and each 

 interambulacral area is divided into three flattened or slightly con- 

 cave bands, widest at the ambitus, narrowing upward toward the 

 apex, and the test is slightly humped above the periproct. Dimen- 

 sions of the holotype: Length, 58 mm.; width, 53 mm., height, 

 31 mm. 



The ambulacra are moderately broad in the petaloidal portions, 

 become narrow at the lower ends of the petals, broaden out toward 

 the ambitus, narrow down again on the base as they approach the 

 peristome, near which they again broaden out sharply to form the 

 floscelles. In the petals the pores are small, and the pairs are con- 

 nected by very narrow furrows, much narrower than the intervening 

 ridges ; the inner pore is slightly elongated, but in deeply weathered 

 specimens is seen to be not quite so long as the outer one ; the pairs 

 of pores are very closely spaced and trend obliquely downward 

 away from the center of the petals, and the petals are almost closed 

 at their lower ends; below the petals very small pores can be dis- 

 cerned on the ambulacral plates all the way to the floscelles. The 

 floscelles broaden out sharply and are composed of long narrow 

 more or less irregular plates each with a pore near its outer end; 

 seven or eight pores on either side of each floscelle form an arch 

 broken above by a group of six or seven pores on irregular plates, 

 which form a small imperfect minor arch sunken considerably below 

 the crest of the main arch. Pores occur on the inner ends of some of 

 the plates of the floscelles, and form an irregular double line of 

 five or six pores. 



