314 Verrill, JVbtes on Radiata. 



This species is allied to M. hexapora of the West Indies, but the 

 latter is very distinct in the form of the posterior perforation, which 

 is mvich more elongated and narrow, in adult specimens; in the 

 ambulacral perforations, which are longer and larger ; in the smaller 

 number a:id larger size of the plates of the upper surface; in the 

 longer spines of the upper surface, which have smaller tips ; in the 

 broader posterior-ambulacral rays ; and in the more angular outline, 

 which is distinctly truncate posteriorly. 



Mr, A. Agassiz has mentioned by name M. longifissa Mich.,* as 

 coming from Panama (Bulletin M. C. Z.), but whether his specimens 

 are the same as the species here described I am unable to say, not 

 having seen them. Dr. Ltitken refers 31. longifissa Mich., described 

 without locality, to 31. pe7itapora, with which it appears to agree far 

 more nearly than with 31. Pacifica. If the specimens of Mr. Agassiz 

 prove to be distinct from our own, they probably will belong to a 

 Pacific representative of 31. pentapora, while 31. Pacifica is the ana- 

 logue of 31. hexapora. 



StoloniclypeUS rotundns A. Agassiz, Bulletin M. C. Z., p. 25, 1 863. 



Clypeader i?^7se^■ Ltitken, op. cit, p. 132. 1864. 



Mr. Bradley collected numerous specimens of this species in Pan- 

 ama Bay, on shelly bottom in 6 to 8 fathoms, with Encope occidentalis 

 and Lytechlniis roseus. Mr. Agassiz collected his specimens at Aca- 

 pulco. Dr. Liltken's example was from Panama. 



One of the largest specimens is 5*4 inches in its longest diameter; 

 4*9 broad at the middle ; *75 high at center ; "3 at margin ; from center 

 to end of posterior lateral ambulacral rays 1*52; breadth of same "8; 

 of median area •52 ; center to posterior margin 2"8 ; to anterior mar- 

 gin 2 '6 The test is thin, somewhat oblong, depressed, except at the 

 center, which is a little elevated. The margin is slightly undulated, 

 curving somewhat inward at the interambulacral zones, and extend- 

 ing farther out in broad, slightly prominent lobes at the ambulacra, 

 which are about three times as broad as the interambulacra at the 

 margin. The posterior portion of the test is somewhat broader than 

 the antei'ior ; a slight lobe on the posterior margin, opposite the anal 

 opening, which is circular and close to the edge. Ambulacral rays 

 broad, subequal, forming a very regular rosette. The anterior one 

 slightly narrowei", and the anterior lateral pair slightly shorter than 

 the posterior pair. The genital pores are close to the center, in the 

 angles of a small pentagon. The ocular openings are scarcely visi- 



* Specimens of this species have been received from Gulf of California and Nica- 

 ragua, — Reprint 



