90 CAUFOHNIA ACADEMY OF SCIENCES. 



As stilted ill the present (U'.scri|)ti()ii, (lie |>:ili of /'. /mlroensis are not lohed mid 

 ihiir )naigins (ire tiifirv. 



These comparit-Dii-; will show how sliikiii^ly difTerent the |iii'sciil species is 

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



HCHINODERMATA. 



Class ECHINOIDEA.' 

 Subclass EUECIIINOIDEA. 



Order DIADI'MATOIDA. 



Suborder STEREOSOMATA. 



Family 11. ECHlNOMETlilD.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 

 jjrimary 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, Hull. .Mus. Comp. Zool., Vol. i, \%bj,{fidc Clark.) 



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

 this species have been found in the lower San Pedro series of Deadman Lsland. The 

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

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



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



Pleistocene. — San Pedro (Arnold). 



6. Strongylocentrotus purpuratus Slimpwn. 



Echinus purpuraliis Stimpson, Crustacea and Echinoderms of the Pacific Coast, 1857 (^fidc 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 



< Tba cluslficition and generic deacripUous for thia clacs an (torn Eastman In Zitters Text Book of Paleontology. 



