PART 5 A MONOGRAPH OF THE EXISTING CRINOIDS 695 



Syzygies occur between brachials 3+4, 9+10, and 14+15 or 15 + 16, and distally 

 at intervals of from 3 to 5, usually 4, muscular articulations. 



Carpenter says that in the types the pinnules are much broken, but the proximal 

 ones seem to have been slender and delicate. 



Locality .Challenger station 244; northeast of Midway Island (lat. 3522' N., 

 long. 169 53' E.); 5301 meters; temperature 1.83 C.; red clay; June 28, 1875 [P. H. 

 Carpenter, 1888] (2, B.M.). 



Remarks. The specific name abyssicola used by Carpenter for the two specimens 

 from Challenger station 244 and also the one from Challenger station 160 was restricted 

 in 1908 so as to cover only the former. 



Station 244 was chosen as the type locality for the reason that in the place where 

 the characters of abyssicola were first mentioned (in the key to the species of the" Tenella 

 group") the only feature given was the number of cirrus segments, and the single speci- 

 men from station 160 had no cirri. 



Genus RETIOMETRA A. H. Clark 



Retiomelra A. H. CLARK, Proc. U.S. Nat. Mus., vol. 83, 1936, p. 248 (diagnosis; type species R. alas- 

 eana sp. nov.). GISLN, Rep. Swedish Deep Sea Exped., vol. 2, Zool., No. 4, 1951, p. 55. 



Diagnosis.- A genus of the Bathymetrinae, in which the centrodorsal is low 

 hemispherical; the numerous cirri are short with up to 20 segments, of which the longest 

 are about three tunes as long as broad and the distal are a little longer than broad; 

 the brachials have slightly produced and spinous distal ends; PI is much elongated, 

 considerably longer than the genital P 2 , and is composed of 20 to 30 segments; there is 

 no marsupium on the genital pinnules. 



Type species.- -Retiometra alascana A. H. Clark, 1936. 



Geographical range. Southeastern part of the Bering Sea and the Gulf of Alaska. 



Bathymetrical range. From 291 to 1270 meters. 



Remarks [by A.M.C.].- A comparison of the type specimens of R. alascana and 

 Antedon exigua P. H. Carpenter has convinced me that the two are not congeneric. 

 The centrodorsal is much higher in exigua with only a small roughened area free of 

 sockets, rather than a large smooth dorsal pole; the cirri, though superficially alike in 

 number of segments and their proportions, differ in their distinct distal enlargement in 

 exigua; the axillaries and second brachials have very slight proximal angles in alascana 

 but prominent ones in exigua, and the oral pinnules, though similarly elongate, have 

 much more flared segments in exigua. I am transferring Carpenter's species to the 

 genus Phrixometra although in the absence of female specimens the presence of brood 

 pouches on the genital pinnules, characteristic of that genus, cannot be ascertained. 

 The three known species of Phrixometra are also from the Southern Ocean (or South 

 Atlantic). A. exigua agrees with them in the form of the cirri, though the segments are 

 relatively longer, in the shapes of the division series and in the flared pinnule segments. 



RETIOMETRA ALASCANA A. H. Clark 



FIGURE 44 



Reliometra alascana A. H. CLARK, Proc. U.S. Nat. Mus., vol. 83, 1936, p. 248 (description; Albatross 

 sta. 3330; southeastern Bering Sea and Gulf of Alaska; 291 [7197] 1270 meters). BARANOVA, 

 Invest. Far-East Seas U.S.S.R., No. 4, 1957, p. 152 (occurrence in Bering Sea; distribution), 

 p. 248. 



