PART 5 A MONOGRAPH OF THE EXISTING CRINOIDS 461 



Deposits along the sides of the ambulacra! grooves of the pinnules are present in 

 all the species; these consist of straight or slightly bent rods sometimes roughened at 

 the ends, which are usually short, rarely long, and may be either stout or slender. 



In Hypalometra the tentacles contain a thin line of spicules placed end to end 

 which runs nearly to their tips. Similar spicules have also been observed in two species 

 of Perometra. 



Relationships. -The genera of Perometrinae seem to be all very closely related to 

 each other. As a group the Perometrinae seem to represent an offshoot from the 

 Bathymetrinae which has become adapted to a comparatively warm habitat and has 

 acquired a considerable resemblance in certain features to the 10-armed genera of 

 C olobometridae. 



KEY TO THE GENERA OF PEROMETRINAE* 



a 1 . PI and P. absent; size small, the 10 arms being from 25 mm. to 35 mm. (usually between 25 mm. 

 and 30 mm.) in length; cirri XX-XXX, 22-25, 10 mm. long (Straits of Florida; 60-386 me- 

 ters) Hypalometra (p. 487) 



a'. PI always present, though P. is sometimes absent. 



&'. Elements of the IBr series and first 2 brachials with smooth and straight borders, laterally in 

 close apposition with their neighbors and sharply flattened against them; synarthrial tuber- 

 cles very prominent, sometimes extravagantly developed (figs. 19 and 21, pp. 463, 471); 10-15 + 

 (usually 10) arms (Madagascar to the Kei Islands and southern Japan; 71-256 [7278] me- 

 ters) Perometra (p. 461) 



b*. Elements of the IBr series and first 2 brachials never with sharply flattened sides, though they 

 may be just in contact laterally; their lateral borders alwavs bear tubercles, one or several 

 to each ossicle, and their distal and proximal borders are usually prominently everted and 

 tubercular. 



c 1 . Interradial and interbrachial portions of the perisome naked; P. always present (Kei Islands 

 and Celebes to southern Japan and north of Tasmania; 122-1040 meters). 



Nanometra (p. 478) 



c 1 . Interradial and interbrachial portions of the perisome with numerous prominent rounded 

 calcareous nodules which are not in lateral contact; P. usually absent (Moluccas and Kei 

 Islands to southern Japan; 100 [?95]-274 meters) Erythrometra (p. 473) 



Genus PEROMETRA A. H. Clark 



Anledon (part) P. H. CARPENTER, Proc. Roy. Soc., vol. 28, 1879, p. 384, and following authors. 



Nanometra (part) A. H. CLARK, Smithsonian Misc. Coll., vol. 50, pt. 3, 1907, p. 349. 



Perometra A. H. CLARK, Smithsonian Misc. Coll., vol. 50, pt. 3, 1907, p. 357 (diagnosis; type species 

 Antedon diomedeae A. H. Clark, 1907) ; Bull. Mus. Comp. Zool., vol. 51, No. 8, 1908, p. 248 (same): 

 Proc. Biol. Soc. Washington, vol. 21, 1908, p. 134 (pinnulation), p. 136 (referred to Antedonidae); 

 Proc. U.S. Nat. Mus., vol. 34, 1908, p. 211 (referred to Antedonidae, restricted), p. 212 (occurs 

 in Japan); Amer. Nat., vol. 42, No. 500, 1908, p. 541 (only known from Indo-Pacific-Japanese 

 area); No. 503, p. 725 (color); Geogr. Journ., vol. 32, No. 6, 1908, p. 602 (characteristic of Indo- 

 Pacific-Japanese region); Proc. Biol. Soc. Washington, vol. 22, 1909, p. 176 (referred to Pero- 

 metrinae); Amer. Nat., vol. 43, 1909, p. 580 (pinnulation); Proc. U.S. Xat. Mus., vol. 36, 1909, 

 p. 362 (deficient pinnulation like that of Comalilia) ; vol. 40, 1911, p. 13 (common to southeastern 

 Africa and the Bay of Bengal, but not occurring in the Arabian Sea) ; Crinoids of the Indian 

 Ocean, 1912, p. 11 (occurs both east and west of Ceylon), p. 12 (represented in the southeastern 

 African region), p. 14 (corresponds to the West Indian Hypalometra), p. 26 (range; covers the 

 range of the subfamily in the East Indian region), pp. 61, 63 (in keys), p. 232 (original reference; 

 type); Die Crinoiden der Antarktis, 1915, p. 181 (range; represented in the Atlantic by Hypalo- 

 melra); Journ. Washington Acad. Sci., vol. 7, 1917, No. 5, p.- 127 (referred to Perometrinae); 

 No. 16, p. 507 (in key; range); Unstalked crinoids of the Siboga-Exped., 1918, p. 234 (in key; 



*See also Addenda (p. 839) for 1967. 



