ClarL — New Genera of Unstalked Crinoids. 133 



Hypalometra gen. nov. 



Genotype. — Antedon dejecta P. H. Carpenter, 1888. 



Radial faces longer than broad, the muscular fossa? large, the notch 

 between them broad, but very shallow. Centro-dorsal hemispherical, or 

 more or less sub-conical, thickly covered with cirri, a small polar area 

 bare. Cirri twenty to thirty, with twenty to twenty-five joints, one or 

 two of the basal about three times as long as wide, thence decreasing 

 distally, the joints in the terminal half being squarish; no dorsal spines; 

 opposing spine well developed. Eadials visible, not extending much 

 beyond the edge of the centro-dorsal ; costals moderately long, well 

 rounded, and widely separated laterally. Ten arms of rather long joints. 

 First exterior and first interior pinnule absent; the lowest pinnule is that 

 of the fifth brachial, which is borne on the outside of the arm; it is 

 composed of (except the basal) elongate joints, and bears a genital gland ; 

 the following \ innules decrease in length, then increase again distally. 



Color (in spirits). — White, the arms sometimes crossed with narrow 

 transverse brown bands. 



Geogra)dii<- distribution.— Caribbean Sea, north to Florida. 



Depth.— 77 to 242 fathoms (Carpenter). 



The hemispherical centro-dorsal bearing numerous cirri which have a 

 moderate number of joints, elongate proximally, squarish distally, com- 

 bined with the entire absence of oral pinnules (the lowest pinnule bear- 

 ing a genital gland) distinguish this genus at once from all others. The 

 only known species is the common 



Hypalometra defecta (P. H. Carpenter). 



Isometra gen. nov. 



Genotype. — Antedon lineata P. H. Carpenter, 1888. 



Centro-dorsal hemispherical or sub-conical, almost completely covered 

 with cirrus sockets. Cirri about twenty-five in number with about thirty 

 joints, subequal, approximately squarish, overlapping dorsally, the distal 

 sometimes with more or less developed spines. Radials about even with 

 the edge of the centro-dorsal ; first costals oblong, about twice as broad as 

 long; costal axillaries pentagonal, wider than long; the costals are 

 rounded and entirely separated from each other. Ten smooth arms; 

 brachials at first oblong or slightly wedge-shaped, broader than long, 

 then becoming more obliquely wedge-shaped and as long # as, or longer 

 than, wide, becoming elongate distally. First two or three pinnules 

 slender, "styliform," with elongate joints; following (genital) pinnules 

 with the third and fourth joints expanded and broadly V-shaped. 



Geographic distribution. — Only known from the south Atlantic, off 

 Uruguay. 



Depth.— 600 fathoms. 



This genus is readily distinguishable from all the other genera of 

 Antedonidae by the expanded joints of the genital pinnules. The only 

 known species is, 



Isometra angustipinna (P. H. Carpenter). 



