CLARK : THE ECHINODEKMS OF PERU. 345 



its outer end ; a lunule also in posterior interambulacrum ; mouth 

 with jaws and teeth. 



Size large, 100 mm. and upwards in length ; brown or gray 

 witli a purplish tinge ; width of area enclosed between two 

 branches of an ambulacral furrow on lower surface, where 



widest, .40 or more of its length Encope micropora 



Size small, rarely exceeding 60 mm. in length. 



Anus only 5-6 mm. back of mouth ; color deep green Mellita pacijica 

 Anus 9-10 mm. back of mouth ; color not green . . Mellita stokesii 

 Test not flat, without lunules or notches ; no jaws or teeth. 



Size large, up to 70 mm. ; test somewhat flattened ; some con- 

 spicuous primary spines (or tubercles) on upper surface; 

 anterior petals hardly as long as posterior, each containing a 



somewhat triangular area Lovenia cordiformis 



Size small, rarely exceeding 25 mm. in length ; test about as high 

 as wide ; no conspicuous primaries ; anterior petals narrow, 

 more than twice as long as posterior pair. . . . Agassizia scrobiculata 



Tetrapygus niger. 



Echinus niger G. I. Molina, 1782. Saggio St. Nat. Chili, p. 175. 



Echinocidaris (Tetrapygus) nigra L. Agassiz et E. Desor, 1846. Ann. Sci. Nat., 6. 



p. 354. 

 Arbacia nigra A. Agassiz, 1863. Bull. M. C. Z., 1, p. 20. 

 Tetrapygus niger A. Agassiz and H. L. Clark, 1908. Mem. M. C. Z., 34, p. 73. 



Plate 10, figure 1. 



This is one of the characteristic sea-urchins of the west coast of South America, 

 and may be easily recognized by the very dark color and nearly hemispherical 

 test. It reaches a large size, full-grown specimens being 75 mm. or even more in 

 diameter. It ranges from Payta, Peru, to southern Chile. Dr. Coker met with 

 this species at La Punta, near Callao ; on rocks between tide-lines, Feriol Bay 

 near Chimbote ; on the rocky shores of the Pescadores Islands, where it was abun- 

 dant ; and at Iudependencia Bay, south of Pisco, on the rocky shores of Isla Vieja. 

 Of the last, Dr. Coker' s notes say: "Black, sometimes with a tinge of violet. 

 Local name ' Gallinazos ' or ' Erizos Gallinazos.' ' Gallinazo ' is the turkey-buzzard, 

 but the name is also generally applied to the black sea-urchin." 



Arbacia stellata. 



Echinus stellatus H. D. de Blainville, 1825. Diet. Sci. Nat., 37, p. 76. 

 Arbacia stellata J. E. Gray, 1835. Proc. Zool. Soc. London, p. 38. 



According to Verrill (1867), this common Panamic species occurs at Payta and 

 Zorritos, Peru, but it was not met with by Dr. Coker. Large specimens may be 

 CO mm. in diameter, but most individuals are considerably smaller. 



