Vol. 56.] FOSSIL COKALS AND ECHINI DS OF SOMALILAND. 



41 



V. The Fossil Echinoidea of Somaliland. 

 The collection includes specimens of two species of Echinids. 



Pseudodiadema somaliense, sp. nov. (Text-figs. 4 & 5.) 



D i a gn s i s. — Test small, depressed, circular. Ease flat, rounded 

 above ; ambitus tumid. 



Ambulacra: the pairs of pores are biserial close to the peristome; 



elsewhere the pairs are 

 Fig. 4. — Abaetinal surface of Pseudo- straight and uniserial. 

 diadema somaliense, sp. nov. ( x 4 There are no primary 

 cliam.) tubercles on the ambu- 



lacra ; but in each area 

 are four vertical rows 

 of granules, with some 

 scattered granules of an 

 extra median series. The 

 granules near the pores 

 are larger than the in- 

 ternal series. 



Interambulacra : about 

 seven plates in each ver- 

 tical series ; the plates 

 are of the cidaroid type, 

 and have one primary 

 tubercle each; the tu- 

 bercles of the three 

 uppermost plates are 

 small, the size suddenly 

 increases, and the tu- 

 bercles of the ambital 

 plates are large. The 

 scrobicular circles are 

 complete in the upper 

 plates, but at the 

 ambitus the scrobicu- 

 lar areas are confluent. 

 Outside the scrobicular 

 circles the plates are 

 covered by numerous, 

 crowded granules. Peri- 

 [To show the uppermost ambital interambu- stome large ; roughly 

 lacral plate the plate above it, and the decagonal. Branchial 

 adjacent ambulacral plates. J . *? , 



J L J incisions large. 



Dimensions. — Diameter of test =13 mm.; height of test = 

 6*5 mm.; width of interambulacrum at ambitus =2 mm.; of am- 

 bulacrum at ambitus =5*5 mm. ; diameter of peristome =6*55 mm. 



Distribution. — Bihendula Limestone: Bihendula, south of 

 Berbera. 



Fig. 5. — Part of a specimen of Pseudo- 

 diadema somaliense. ( X 6 diam.) 



