Clarl — A Revision of Thalassometrirlse and Himerometridse. 11 



10. Heterometra gen. nov. 

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



Centro-dorsal discoidal, thin to moderately tliick, tlie dorsal polar area 

 sometimes flat, l)ut nsually more or less convex, the sides sloping, the 

 cirrus sockets arranged in or.e and a partial second to two and a partial 

 third closely crowded alternating rows. 



Cirri xvn-xxx, 20-37, about one-fourth the length of the arms; proxi- 

 mal cirrus joints (except the basal) slightly longer than broad, becoming 

 broader than long distally ; distal cirrus joints always sharply carinate, 

 and usually developing more or less prominent spines. 



Radials but slightly, when at all, visible ; i Brj short, more or less united, 

 but always free distally, rarely reaching a length of one-half the widtli; 

 I Br 2 pentagonal, half again to twice as long as the i Bri, rounded dor- 

 sally, widely free laterally; i Br and division series smooth laterally, 

 without marginal projections; ii Br 4 (o-f4), rarely 2; in Br (when pres- 

 ent) always 2. The development of ii Br and in Br series is irregular, 

 some of the i Br series being always better supi)lied than the others. 



Arms 11 to 28, though usually ratlier less than 20; first few brachials 

 discoidal, then ol)liquely wedge-shaped or triangular, much broader than 

 long, gradually becoming less obliquely wedge-shaped, sometimes almost 

 oblong, and short, though they are never excessively short and discoidal 

 as in Himerometra. 



Pu shorter and more slender than Pj, which, in turn, is shorter and 

 more slender than P,, the last being the largest pinnule on the arm ; lower 

 pinnules stout basally, tapering gradually to a slender and more or less 

 flagellate tip; the enlarged lower part usually more or less stiffened, this 

 stiffening becoming less and less distally. Distal ])innules always much 

 shorter than the enlarged proximal pinnules, usually not much more than 

 one-half as long. 



Color (in spirits). — Light brown to chocolate brown, the perisome 

 usually darker; light grayish brown ; ))lackish brown, with a tinge of red- 

 dish; dull orange, broadly banded with white. 



Distribution. — Ked 8ea eastward (Muscat; Kurrachee; Ceylon; Bay of 

 Bengal) to Amboina and the Philippine Islands. 



Depth. — Littoral, extending down to 24 fathoms. 



The described species referable to this genus are : 

 Heterometra affinis (Hartlaub) 



" bengalensis (Hartlaub) 



" brockii (Hartlaub) 



" quinduplicava (P. H. Carpenter) 



" reynaudi (J. Mliller) 



" savignii (J. Midler). 



From the two other genera which have the ii Br series 4 (3-F4) Hete- 

 rometra may be very readily distinguished. Himerometra always has the 

 brachials exceedingly short and discoidal, usually a much larger number 

 of arms, and Pu longer and stouter than P^ or Pj, which, again, are 

 longer and stouter than the succeeding pinnules ; the in Br series, always 



