A. H. CLARK : THE CRINOIDS OF THE INDIAN OCEAN. 323 



slender than the others, and all the cirrus segments beyond the second are 

 about as long as broad. 



It is only within a very few months that these little species which compose 

 the subgenus Prometra have been recognized at all. It was in 1908 that the first 

 two known species were recorded, both misidentified, and both referred to previ- 

 ously described species of Oligometra. Chadwick listed Oligometra serripin7ia from 

 Suez Bay in 10 fathoms, and I recorded a supposed second specimen of Oligometra 

 japonica from Sagami Bay in 55 fathoms. I received in exchange a specimen of 

 Mr. Chadwick's Oligometra serripinna from Suez, and immediately recognized it 

 as a new species of Colohometra, describing it as such. Later I compared my sup- 

 posed specimen of Oligometra japonica with Hartlaub's type (in the Berlin 

 Museum) and for the first time noticed the absence of P^ in my example. The 

 type of C. (P.) hrevicirra I for a long time thought was an aberrant individual of 

 Oligometra serripinna; it did not quite agree with any of the other specimens 

 at hand, and was therefore put aside awaiting the receipt of additional material 

 which might throw some light vipon it. The discovery that my supposed 

 Oligometra japonica was really a Colohometra led me to re-examine this specimen, 

 and I found that in reality it was a Colohometra and not an Oligometra at all. It is 

 very evident, therefore, that the greatest care must be used in the identification 

 of the species of Oligometra for, though all the species of that genus differ mdely 

 from the species of Prometra in minute detail, the species of the latter are 

 superficially so very similar to those of the former as to be in danger of reference 

 not only to that genus but to particular species in it. 



A further complication has recently come to light ; one of the specimens in 

 the type series of Oligometra serripinna var. erinacea lacks P^ on both arms of 

 one of the rays, and two specimens of Oligometra gracilicirra which I have recently 

 examined lack P^ on all the arms, though all the specimens I had previously 

 seen, including the type, had it present in all cases. 



Taking other recent discoveries into consideration it has now become 

 evident that the genera of the Colobometridae, all very distinct in their t}rpical 

 forms, in their more generalized types grade so insensibly into each other as to 

 be with difficulty distinguishable. 



OLIGOMETRA SERRIPINNA. 



LOCALITY.— 0^ Gopalpore ; 25—28 fathoms.— Two specimens. 



Same Locality ; 30 — 38 fathoms. — Two specimens. 



Remarks.— The two specimens from 25—28 fathoms have the lateral pro- 

 cesses on the segments of the lower pinnules long, curved and hook-like; the 

 segments of the lower pinnules other than those which are enlarged are 

 produced and spinous. One of the specimens has an arm length of 65 mm. ; 

 the other is slightly smaller. 



Both of the specimens from 30—38 fathoms liave an arm length of 60 nuu. 



