90 CALIFOENIA ACADEMY OF SCIENCES. 



As stated in the present description, the pali of P. pedroensis are not lohecl and 

 their margins are entire. 



These comparisons will show how strikingly different the present species is 

 from any of those previously described species from the west coast of North America. 



ECHINODERMATA. 



Class ECHINOIDEA/ 



Subclass EUECHINOIDEA. 



Order DIADEM ATOI DA. 



Suborder STEREOSOMATA. 



Family II. ECHINOMETRID^E. 



Genus Strongylocentrotus Brandt. 



Test symmetrical and polyporus. Amb straight, broad at the ambitus and peristome, and with 

 broad, poriferous zones. Pairs of pores in oblique arcs, or almost transverse series of from four to 

 ten pairs, and crowded actinally. Interporiferous areas with two vertical rows of plain, imperforate 

 primary tubercles ; secondaries and miliaries also present. Amb with two rows of primary, and four 

 or more of secondary tubercles. 



5. Strongylocentrotus franciscanus A. Agassiz. 

 Toxocidaris franciscana A. Agassiz, Bull. Mus. Comp. Zool., Vol. i, 1863 ijide Clark.) 



This is the large sea-urchin of the West Coast. Spines which are probably of 

 this species have been found in tlie lower San Pedro series of Deadman Island. The 

 spines of this species are distinguishable by their large size and longitudinal striations. 

 Some of the spines found are 20 mm. long and o mm. in diameter. 



Living. — Puget Sound; San Diego (H. L. Clark). 



Pleistocene. — San Pedro (Arnold). 



6. Strongylocentrotus purpuratus Siimpson. 



Echinus purpuraius Stimpson, Crustacea and Echinoderms of the Pacific Coast, 1857 {,fide Clark.) 



Numerous spines of this small purple sea-urchin have been found in the San 

 Pedro series. No part of the test has ever been discovered in these deposits, to the 

 writer's knowledge. Several nearly perfect tests of this species were found in the 



* The classlficatiou auU geueric descriptious for tblsclaes are ftoui Eaetmau iu Zittel's Text Book of Paleoutology. 



