Clark — A Revision of Thalassometridae and Himerometridse . 21 



more or less produced, incising the first costals; ii Br usually 4 (3 + 4), 

 more rarely 2; crei^erally l)oth types occur in every specimen, but the 

 former in the majority; in Br, when present, 2(1 + 2), developed interi- 

 orly in ], 2, 2, ] order. The i Br, further division series, and lower 

 brachials are in close a]j})Osition, and are sharjily flattened laterally; tliey 

 are somewhat convex dorsally, and occasionally so much so as to expose 

 the distal edge of ?„. 



Arms 10 to 38, but usually 20 or over, rounded dorsally, and laterally 

 compressed in the ])roximal third; first twelve or fourteen brachials 

 oblong, about twice as broad as long, then becoming triangular, nearly 

 as long as broad, and in the terminal portion of the arm ol>li(iueIy wedge- 

 sh.aped and longer than broad. 



Pr, and Pi slender, composed of twenty to forty short joints; Pg about 

 the same size, with slightly larger joints; following pinnules with larger 

 joints, some of which are laterally expanded to protect the genital glands; 

 this expansion is never excessive, and is often slight; it is always regular 

 and even, beginning gradually and dying away more gradually toward 

 the distal portion of the pinnule, which last is always delicate. The pin- 

 nule following P, may remain of the same length as Pj for some time, may 

 increase slightly in length, or tliere may be a slight decrease to Pg, after 

 which they increase again ; the distal pinnules are comparatively short, 

 not exceeding Pj in length, and usually somewhat shorter. 



Color. — Clear yellow to brownish yellow or yellow-brown; calyx and 

 arm bases to the first syzygy often nuich darker than the rest of the 

 animal. 



Distribution. — East London, South Africa, eastward through the Indian 

 Ocean to the Sahul Bank, the Meangis, Kermadec, and Ki Islands, north- 

 ward to the Philippines and Japan. 



Depth. — 140 to 630 fathoms; most commonly found below 300 fathoms.* 

 Included species: 



Pacliylometra aiigusticajyx (P. H. Carpenter) 

 " disiinrtd (P. H. Carjienter) 



" flexilw (P. H. Carpenter) 



" inscqualis (P. H. Carpenter) 



" palula (P. H. Carpenter) 



" rohusta (P. H. Carpenter) 



" sdateri (Bell) 



smithi (A. H. Clark). 



23. Chlorometra gen. nov. 



Genotype. — Antedon garrettiana A. H. Clark, 1007. 



Centro-dorsalsubconical, moderate or small, the cirrus sockets in one or 

 two more or less definite columns in each radial area. 



Cirri xv, 16-18, nearly one-third of the arm length; first three joints 



*One species is doubtfully recorrted from near Kandavu, Fiji, in 255, (ilO. or 210 fathoms, 

 and from the same locality in 1350 fathoms; tlie first is too uncertain to be depended 

 upon, the second is so much deeper than the lowest unuuestionable record that further 

 evidence is needed before it can be accepted. 



