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FOUR NEW FJRITTLESTARS FROM PUERTO RICO 



By AUSTIN H. CLARK 

 Curator, Division of Echinoderms, U. S. Natioiutl Museum 



(With Threk Plates) 



Among the numerous brittlestars oljtained by the First Johnson- 

 Smithsonian Deep-Sea Expedition are three new species of the genus 

 Ophiomusiuin, two of which are interesting in Iiaving the upper of 

 the two arm spines transformed into a hook curving outward from 

 the arm. There is also a new species of Ophiocircc, a genus of the 

 family Ophioleucidae known heretofore only from the Philippine 

 and Lesser Sunda Islands. 



OPHIOMUSIUM REGULARE, n. sp. 



Plate I, figs. I, 2 



Locality. — Caroline station 45 ; west of Puerto Rico (lat. i8°03'45" 

 N., long. 67°48'io" W.) ; 240 to 300 fathoms; February 11, 1933. 

 Eighteen specimens (U.S.N.M. nos. E.5194 [type] and E.5195). 



Description. — The disk is pentagonal, slightly elevated centrally, 

 8 mm in diameter, and the slender arms are 28 mm long. The plates 

 on the aboral surface of the disk are few in number. 



The center of the disk is occupied by a central plate surrounded by 

 five somewhat larger plates radially placed, between the bases of 

 vv'hich, and adjoining the central plate, are five small triangular plates. 

 From the outer edge of the radially placed plates to the arm base, 

 separating the radial shields, runs a rather narrow row of four plates, 

 the sides of this row converging for two-thirds of the distance to the 

 arm base and then, on the last two plates, diverging again. In this 

 row the innermost plate is the largest, the second is slightly to con- 

 siderably shorter, the third is small, less than half the length of the 

 second, and the fourth is somewhat longer than, and about twice as 

 broad as, the third. On either side of the last (fourth) plate a band 

 of low crowded papillae in three to four rows, which is nearly as 

 broad as the length of the plate, separates the distal ends of the 



Smithsonian Miscellaneous Collections, Vol. 91, No. 24 



