1920] Kew: Cretaceous and Cenozoic Echinoidea 



57 



Family STRONGYLOCENTROTIDAE Gregory 

 Genus STRONGYLOCENTROTUS Brandt 



STRONGYLOCENTROTUS FRANCISCANUS A. Agassiz 

 Plate 4, figures la, Ih, Ic 



Toxocidaris franciscana A. Agassiz. Bull. Mas. Comp. Zool., vol. 1, 1863, 

 p. 22. 



Toxocidaris glohosa A. Agassiz. Proc. Aead. Nat. Sci. Phila., vol. 15, 

 1863, p. 356. 



Strongylocentrotus franciscanus A. Agassiz. Rev. Ecli., 111. Cat. Mus. 

 Comp. Zool., pt. 1, 1872, p. 163; pt. 3, 1872, p. 442, pi. 5b, figs. 1-2, 

 pi. 7, figs. 10, 10a. 



Strongylocentrotus franciscanus. Arnold, Calif. Acad. Sci. Mem., vol. 3, 

 1903, p. 90. 



Strongylocentrotus franciscanus. Stefanini, Boll. Soe. geol. ital., vol. 30, 

 1911, p. 706. 



Strongylocentrotus franciscanus. Clark and Twitchell, U. S. Geol. Surv. 

 Mon., vol. 54, 1915, p. 223. 



Figxtred specimen. — No. 11389 Univ. Calif. Coll. Invert. Pal. 



This specimen is of rather small size. Measurements: greatest 

 diameter 38.7 mm., greatest thickness 16 mm. Two main vertical rows 

 of large tubercles in the interambulacral areas which occupy the 

 greater part of the plate ; two short rows of smaller tubercles near 

 the median line, and a row along the border of this area ; other smaller 

 secondaries are present. Ambulacral areas contain two rows of pri- 

 maries, smaller in size than those of the interambulacral areas ; a 

 median row between the primaries and a row of secondaries in each 

 poriferous area are present. Arcs of pores oblique and contain as 

 many as nine pairs. Both upper and lower surfaces considerably 

 flattened. 



Arnold, in discussing its occurrence on the Pacific Coast, says : 



This is the large sea urchin of the west coast. Spines which are probably 

 of this s])ecies have been found in the lower San Pedro series of Deadman Island. 

 The spines of this sjjecies are distinguishable by their large size and longitudinal 

 striations. Some of the spines are 20 millimeters long and 3 millimeters in 

 diameter. 



Geologic horizon. — Upper Fernando formation. Upper Pliocene; 

 associated with Dendrastcr diegocnsis subsp. venturaensis Kew. San 

 Pedro formation (lower part). Pleistocene; Recent. 



Localities. — Las Posas Hills, Ventura County, California, fig- 

 ured specimen ; San Pedro, Los Angeles County, California ; Fourth 

 and Hill streets, Los Angeles, California (Moody). 



