1923] Clark, Echinoderms fro?n Lower California 159 



rial is due to the peeling off and loss of the red epidermis, which 

 appears to flake off and disappear very easily. A very constant feature 

 of the coloration of pulvinata, conspicuous in all but one of the present 

 series, is a yellowish triangular spot in each interradius just above the 

 ambitus. This is usually visible even in the greenish specimens and is 

 very noticeable in the red ones. Apparently this spot is pale yellow, or 

 possibly even white, in life. 



San Francisquito Bay, east coast of Lower California. 



Fifteen specimens. 



Arbacia incisa (A. Agassi z) 

 Echinocidaris incisa A. Agassiz, 1863, Bull. Mus. Comp. Zool., I, p. 20. 

 Arbacia incisa H. L. Clark, 1913, Bull. American Mus. Nat. Hist., XXXII, 

 p. 220. 



There is a fine series of this species in the present collection, for the 

 most part in good condition. They range from 10 to 38 mm. in diameter. 

 The relative length of the primary spines shows some diversity; in the 

 individual with the test 38 mm. h.d., the spines are 39 mm. long, but in 

 one having h.d. 16 mm. the spines are 23 mm. long. Half a dozen of the 

 specimens lack a locality label but the others are from San Francisquito 

 Bay, east coast of Lower California. 



Twenty specimens. 



Clypeaster speciosus Verrill 



Clypeaster speciosus Verrill, 1870, American Journ. Sci., (2) XLIX, p. 95. 



This fine clypeastroid was not represented in the first collection, 



but beautifully preserved specimens are now at hand, 76 mm. long, 66 



mm. wide and 18 mm. high. They have the lower side very flat and the 



color is a deep, dull purple. 



San Esteban Island, Gulf of California. 

 Two specimens. 



Encope californica Verrill 



Encope californica Verrill, 1871, Trans. Connecticut Acad. Sci., I, p. 586. 



This remarkable clypeastroid was also wanting in the earlier collec- 

 tion, although two other species of Encope were represented. The three 

 species are easily distinguished from each other and show no tendency 

 to intergrade or hybridize. It is possible that they do not occur 

 together at any given place, but that each species has its own particular 

 habitat. The 'Albatross' collections indicate that californica and 

 grandis occur at the same locality and that grandis and micropora are 



