A MONOGRAPH OF THE EXISTING CRINOIDS 117 



History. The first known species of this genus was described under the name of 

 Antedon perspinosa by Dr. P. H. Carpenter in 1881. In my first revision of the old 

 genus Antedon published in 1907 perspinosa was referred to the new genus Cyllometra, 

 and in 1909 it was made the type of the new genus Colobometra, which included also 

 C. suavis. In 1912 Colobometra chadwicki, which had been described by me in 1911, 

 was referred to a new subgenus Prometra, together with Colobometra (Prometra) 

 owstoni and a new species C. (P.) brevicirra. In 1918 Prometra was definitely sep- 

 arated from Colobometra, and is herein considered as a synonym of Decametra. The 

 two species owstoni and longipinna, heretofore referred to Prometra, are herein assigned 

 to the new genus Alisometra. 



KEY TO THE SPECIES IN THE GENUS COLOBOMETRA 



a 1 . Cirri very long with about 60 (53-65) segments of which the longest are about one-third again 

 as long as broad; Pa slightly larger than P 2 ; following pinnules to Pe or PS similar, decreasing 

 slightly in length; arms 120-150 mm. long (Fiji, Lord Howe Island and Port Denison, Queens- 

 land, north to northern New Guinea [Jobi] and westward to the Paternoster Islands; 0-31 



[?36] meters) perspinosa (p. 117.) 



a 2 . Cirri shorter, with not more than 53 segments; P 3 only exceptionally longer than P 2 . 



&'. Cirri with 35-53 (usually 45-50) segments of which the longest are usually not so long as 

 broad, rarely slightly longer than broad; P 3 similar to P 2 and of the same length, rarely 

 slightly longer; arms 110-170 mm. long (Philippine Islands to Singapore and southward to 



Amboina; littoral) vepretum (p. 124.) 



b 2 . Only exceptionally more than 40 cirrus segments, of which the longest are longer than broad. 

 c 1 . Pj markedly longer and stouter than the pinnules following, very stiff and spinelike; Pa sim- 

 ilar to Pj but shorter and more slender; 29-40 (usually 30-35, very exceptionally more 

 than 40) cirrus segments; arms 40-105 (usually 45-80) mm. long (Philippine Islands 

 south to the Moluccas and the Lesser Sunda Islands, and westward to Ceylon; 42 [?27] 



-106 meters) discolor (p. 128.) 



c 2 . Pj to PS or P; approximately equal in length and stoutness. 



d l . PI much less stiff than P 2 , with none of the component segments more than very slightly 

 longer than broad; P 2 to P? approximately equal in length and similar, with only a very 

 slight development of spines on the distal borders of the component segments. 

 e l . The 18-22 cirrus segments before the penultimate bear single median dorsal spines; 



P, has 21 segments (Philippine Islands; 36-42 meters) suavis (p. 132.) 



e 2 . The 3 or 4 cirrusse gments before the penultimate bear siuglem edian dorsals pines, 



PI has 14 or 15 segments (Red Sea; 55 meters) arabica (p. 132.). 



d 2 . P! resembles P 2 and is stiff and spinelike, composed of 10 segments of which the fourth 

 and following are about four times as long as broad; only the antepenultimate cirrus 

 segment bears a single median dorsal spine; P 2 to P s similar and of approximately 

 equal length (Solomon Islands) diadexna (p. 133.) 



COLOBOMETRA PERSPINOSA (P. H. Carpenter) 



PLATE 14, FIGURES 67-69 



Antedon perspinosa P. H. CARPENTER, Notes Leyden Mus., vol. 3, 1881, p. 178 (description; Jobie). 

 BELL, Proc. Zool. Soc. London, 1882, p. 533 (listed), p. 534 (specific formula). P. H. CAR- 

 PENTER, Proc. Zool. Soc. London, 1882, 1883, p. 746 (specific formula); Challenger Reports, 

 Zoology, vol. 26, pt. 60, 1888, pp. 54, 193, 366, 378. HARTLAUB, Nova Acta Acad. German., 

 vol. 58, No. 1, 1891, p. 85 (Antedon loveni Bell, 1884, a synonym; type lacks P. [specimen from 

 Amboina described and figured is C. vepretum]). HAMANN, Bronns Klassen und Ordnungen des 

 Tier-Reichs, vol. 2, Abt. 3, 1907, p. 1579 (listed). A. H. CLARK, Proc. U. S. Nat. Mus., vol. 

 39, 1911, p. 562 (P. absent, though this not noticed by Carpenter); Notes Leyden Mus., vol. 

 33, 1911, p. 176 (notes on the type); Mem. Australian Mus., vol. 4, 1911, p. 713 (history); 

 p. 719 (found by Hartlaub to include Antedon insignis Bell, 1882, and A. loveni Bell, 1884); 



