Verrill, JV^otes on liadiata. 301 



This species is readily distinguished from E. stellata by much more 

 numerous, more crowded, and smaller interambulacral tubercles ; by 

 the narrower and more numerous plates ; by the much smaller genital 

 plates, which are outwardly obtuse instead of acute, so that they do 

 not form a well marked star, and are broader than long, while in E. 

 stellata they are longer than broad. The lateral union of the genital 

 plates in front of the ocular plates is a good distinctive character for 

 the latter species, as well as the greater size of the abactinal star ; 

 deeper sutures between the plates ; and the variegation of the test. 



This species in some respects corresponds with E. Davisii A. Ag., 

 found from Long Island Sound to Virginia, while E. stellata may be 

 considered the Pacific representative of E. punctulata of the Carolina 

 coast and Florida. 



Arbacia nigra Gray. 



Echinus nigtr Molina, Hist. Nat. du Chili, p. 175. 

 Echinus purpiirescens Val., Voy. Venus, yA. 5, fig. 1, 1846. 

 ? Echinus grandinosu^ Val, op. cit., y>1. 11, fig. 1. 

 Echinocidaris (Tetrapygus) Jiigra Agassiz, Catal. Rais., 1846. 



This species was found at Callao, Peru, in great abundance by Mr. 

 Bradley, thrown upon the beaches, and also living at low-water mark 

 among rocks. It has been recorded from Paita, (Ag. and Desor). 



The Essex Institute has specimens collected at Caldera, Chili, by 

 Capt. W. H. A. Putnam, who also collected it at Mejillones. 



Psammechinus pictus Vemii, sp. nov.* 



A small species with a regularly rounded profile, somewhat hemi- 

 spherical in form, but slightly depressed. Spines slender, moderately 

 long, one fourth the diameter of the test. Actinal region large, 

 nearly one half the diameter of the test, its membrane covered with 

 small irregular scales. Ambiilacral zones about two thirds as broad 

 as interambulacral. Pores in regular arcs of three pairs, which be- 

 come much narrower beneath, Ambulacral tubercles in four series, 

 those of the two exterior relatively large and prominent, not crowded ; 

 between these the miliaries form two somewhat irregular rows. In 

 the poriferous zones a small tubercle separates the successive arcs, 

 forming a regular row of distant tubercles, not larger than the largest 

 miliaries. Interambulacral spaces with two principal rows of tuber- 

 cles, near the exterior, about the same size as the principal ones of 

 the ambulacra. Exterior to these are two outer rows of much smaller 

 tubercles that do not reach the summit ; in the space between the 

 two principal rows similar secondary tubercles are distantly scattered; 

 miliaries numerous around the larger tubercles. Ocular and genital 



* Mr. A. Agassiz thinks this the young of Lytechinus semituhenulatus V., — Reprint. 



