Verrill, JS^otes on liadiata. 307 



always maintained externally, out of wliich the claws of the oral) may 

 be thrust, but is apparently not large enough to allow it to go en- 

 tirely out, when fully grown. By this parasite the anal area is so dis- 

 torted and displaced that among ninety specimens I have not found 

 one in which it is in its natural state, every specimen giving evidence, 

 by distortion or otherwise, of having been infested by it. But as 

 most of these were found dead upon the beach it is probable that they 

 were individuals that had been killed or weakened by the parasite, 

 while specimens unattacked by them may be found in deeper water. 



It is probable that the irregularity or gibbosity of the Eehhius 

 gihbosus Val. was caused by the same or a similar parasite, but 

 whether that name applies to the present species of Euryechinus I 

 am unable to determine, the description being too imperfect for relia- 

 ble ideutitication. But should it pi'ove to be the same, the name is 

 inapplicable, referring only to an accidental, or diseased condition, 

 which is not constant even in the diseased specimens. For these 

 reasons I have thought it necessary to apply a new name to the pres- 

 ent species. 



The original description of JE. gihbosus is as follows :* " Espece 

 irregulit^re voisine de VJE. lividus par les details de son test. Quatre 

 paires de pores leg^rement arquees. Des iles Gallapagos, — Mus., 

 Paris." 



The Euryechinus imbecillis can scarcely be said to be near E. livi- 

 dus in the character of the test, since in the latter there are eight or 

 ten rows of subequal interambulacral tubercles, which are larger and 

 far more numerous than in this species, besides many other diiferen- 

 ces. It approaches much more nearly, in the character of its test and 

 arrangement of its tubercles, E. Drobachiensis and, especially, E. 

 granulatus Verrill, of the coast of New England, but is quite dis- 

 tinct from all, in the thinness of its test ; in its smaller and weaker 

 genital and ocular plates, and larger size of the anal area and, conse- 

 quently, of its abactinal system ; in the flatness of the lower surface 

 and somewhat widened poriferous zones ; fewer tubercles ; and more 

 slender spines. 



Toxopneiistes s^p- 



Toxocidaris mexicana A. Ag., Bulletin M. C. Z., p. 22, 1863, (no description). 



Mr. Agassiz has identified a specimen from Acapulco, in the Mus- 

 eum of Comparative Zoology, as the Ileliocidaris Mexicana Ag. 

 The latter species was originally described (Catal. Rais.) as coming 

 from Vera Cruz. Dr. Ltitken refers it to Echinometra. In our col- 



* Agassiz and Desor, Catal. Rais., in Ann. des Sci., vi, p. 367, 1846. 



