A MONOGRAPH OF THE EXISTING CRINOIDS 49 



Diagnosis.— A genus of Colobometridae including small species with 10 arms 

 20-80 mm. long; the cirri have 24-39 smooth segments, the distal shorter than the 

 proximal, those beyond the proximal fourth bearing long median dorsal spines; the 

 proximal pinnules are rather short and somewhat stiffened, composed of rather short 

 segments with spinous distal ends, and do not differ greatly in length; P2 is the largest, 

 with not more than 13 rather short segments; Pa may or may not be present; the 

 segments of the genital pinnules are not broadened. 



This genus is easily recognized by the rather long cirri of which the segments in 

 the outer three-fourths bear long median dorsal spines, and the short and stiffened 

 proximal pinnules composed of short segments with spinous distal ends. 



Geographical range. — From the Philippine to the Kei and Andaman Islands. 



Bathymetrical range. — From 80 to 113 meters. 



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

 of Oligometra gracilicirra in 1908, and a variety was described as Oligometra gracUicirra 

 var. ornafa in 1911. In 1916 it was made the type of the monotypic genus Cotylo- 

 metra. 



KEY TO THE FORMS IN THE GENUS COTYLOMETRA 



a '. No keel on the IBr series and arms; edges of the elements of the IBr series and first two brachials 

 unmodified (Philippine to the Kei and Andaman Islands; 85-113 meters). 



gracilicirra gracilicirra (p. 49) 



a '. The elements of the IBr series and the brachials in the proximal third of the arm each bear a 

 narrow rounded median keel which on the first brachial may be reduced to a prominent tuber- 

 cle; the outer edges of the ossicles of the IBr series and the first two brachials are bordered 

 with a row of thickly set tubercles or small spines (between Borneo and Palawan; 80-106 

 meters) gracilicirra omata (p. 5) 



COTYLOMETRA GBACILICIRKA GRACILICreRA:(A. H. Clark) 



Plate 8, Figures 38-40; Plate 9, Figures 41, 42 



Oligometra gracilicirra A. H. Clark, Smithsonian Misc. Coll., vol. 52, part 2, 1908, p. 221 (descrip- 

 tion; Albatross station 5153); Proc. Biol. Soc. Washington, vol. 22, 1909, p. 7 (listed), p. 42 

 (compared with O. studeri); Vid. Medd. Nat. Foren. K0benhavn, 1909, p. 179 (compared with 

 0. serripinna) ; Proc. U. S. Nat. Mus., vol. 39, 1911, p. 544 (compared with 0. g. var. ornata); 

 Crinoids of the Indian Ocean, 1912, p. 168 (synonymy; Andaman Islands; notes; previous 

 records), fig. 26, p. 169, p. 323 (2 specimens recorded lacking P. on all the arms). 



Cotylometra gracilicirra A. H. Clark, Journ. Washington Acad. Sci., vol. 6, No. 5, 1916, p. 116 

 (range); Unstalked crinoids of the Siboga-Exped., 1918, p. 70 (compared with Eudiocrinus 

 indivisus), p. 128 (in key; range; notes; stations 260, 305), pp. 275, 276 (listed), pi. 28, fig. 110. 



Diagnostic features.— There are no keels on the IBr series and lower brachials, 

 and the edges of the elements of the IBr series and the first two brachials are unmodi- 

 fied. 



Description.— The centrodorsal is thick discoidal, with the rather large polar 

 area thickly covered with small blunt spines. The cirrus sockets are arranged in 

 a single marginal row. 



The curi are XV, 28-30, 12 mm. in length. The first segment is very short and 

 those following gradually increase in length to the fourth, which is about as long as 

 broad, and after the tenth become very slightly broader than long. The first and 

 following segments have the distal dorsal edge everted, this aversion gradually be- 



