652 BULLETIN 82, UNITED STATES NATIONAL MUSEUM VOLUME 1 



While the cirrus segments in Thaumatometra and Bathymetra are all elongated, 

 those of Orthometra and Tonrometra are all relatively short, though of a different type 

 in each genus. 



Trichometra is peculiar in the constant presence of an abrupt spinous eversion of 

 the distal edges of the earlier brachials, though this condition is approached by species 

 in related genera. 



[Notes by A.M.C] In the typescript, Mr. A. H. Clark had made Phrixometra, 

 including only P. longipivna (P. H. Carpenter), a synonym of Nepiometra. However, 

 John (1938) pointed out that the original description of the pinnules of longipinna and 

 hence the diagnosis of Phrixometra by Mr. Clark (1917), were erroneous, the pinnules 

 following Pj being in fact distinctly different from the first two pinnules and not similar 

 to them. Also Carpenter did not perceive the marsupia. P. longipinna cannot therefore 

 be reconciled \vith the diagnosis of Nepiometra and accordingly I have reinserted the 

 genus Phrixometra. As for Thaumatometra nutrix Mortensen, which was included in 

 Phrixometra by John, together with a new species P. rayneri, Mr. Clark had previously 

 erected a new genus for it in the typescript, which was distinguished by the presence 

 of the marsupium. There is now no distinction between longipinna and nutrix on this 

 count and although nutrix has the genital pinnules similar to the preceding oral ones, 

 vmlike longipinna, P. rayneri is intermediate in tliis respect. A new genus for nutrix 

 therefore appears to be unwarranted and in addition the existing material of these three 

 species is so inadequate that it seems inadvisable to complicate the nomenclatiu"e 

 further. 



I have also included in the genus Phrixometra the species Antedon exigua P. H. 

 Carpenter from off Marion Island in the Southern Ocean. This was included in 

 Retiometra when that genus was described by Mr. Clark in 1936, but a comparison 

 with the type specimen of /?. alascana and with specimens of Phrixometra longipinna 

 has convinced me that exigua is congeneric with the southern rather than the northern 

 species. 



In checking Mr. Clark's key to the genera of this subfamily, I found that most 

 of it no longer holds good according to the data now available, new specimens and 

 species having been described since it was written. The following artificial key was 

 drawn up with some difficulty and I was imable to avoid using several characters, such 

 as the proportions of the cirrus segments and numbers of pinnule segments, which 

 are somewhat variable with size. 



Two species — Tonrometra spinulijera (transferred here from the genus Florometra 

 of the Heliometrinae) and Thaumatometra tenuis — stand so far apart from the other 

 species of Tonrometra and Thaumatometra in the characters used in the key that they 

 have liad to be dealt with separately. Although I have no doubt that spinulijera is 

 congeneric with tlie type species of Tonrometra, T. remota, Thaumatometratenuis is so well 

 marked off from the other species of the genus by the niunerous segments of Pi (about 

 35 as opposed to 10 to 20 in all tiie rest) that I think it should be isolated from them. 

 A new generic name would then be necessary for the other species now included in 

 Thaumatometra since tenuis is itself the t3-pc species. 



It was also found necessary to key out the genus Phrixometra twice over to cover 

 male specimens lacking the characteristic marsupium and, since its species may have 



