186 



BULLETIN 76, UNITED STATES NATIONAL MUSEUM 



is at right angles to the substratum upon which the animal is crawling. There are 

 fewer longiseries of actinaJ plates (which are a little larger) than in ochraceus. 



In young specimens (pi. 79, fig. 4a) the skeleton has a series of wide intervals or 

 spaces adjacent to the superomarginals and the primary dorsolaterals are relatively 

 big. As in ochraceus the carinala lose their 4-Iobed contour later in life. 



Very young specimens (R 14 mm.) have, on the supermarginal plates, a very 

 small area of hyaline bosses. These disappear in specimens with R 18 mm. In 

 young of P. giganteus capitatus the superomarginals have relatively more surface, are 

 more triangular in shape, and these specialized areas cover nearly the whole surface. 

 They are well-marked in the young of ochraceus, having R 22 mm. 



Type of Pisaster brevispinus. — Cat. No. 1285 U.S.N. M. 



Type locality. — Near mouth of San Francisco Bay, Calif., 10 fathoms, sand. 



Distribution.- — Sitka, Alaska (Verrill) to Santa Barbara, Calif.; lowest tide to 

 56 fathoms, sand, or mud and sand. 



Forma brerispinus has been taken in the Puget Sound region, Washington, and 

 from Crescent City to Monterey Bay, Calif. 



Forma paucispinus (type locality, Puget Sound) ranges from Sitka to Santa 

 Barbara. 



Specimens examined. — One hundred and fifteen, in addition to many from Mon- 

 terey Bay. 



Specimens of Pisaster brevispinus examined 



i Feet. 



