316 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



Genus OPHIOCOMINA Kcehler. 12 



Ophiocomidae, with the spines hollow, like those of Ophiacantha; 

 the disk is covered with granules on both surfaces; the mouth shields 

 are transversely broadened; the much-elongated adoral plates are in 

 contact in the median interradial line; they broaden outwardly and 

 more or less widely separate the mouth shield from the first side arm 

 plate; the oral plates are high; the mouth and tooth papillae are 

 arranged as in the genus Ophiocoma. 



Except for the characters shown by the spines there are none which 

 recall the genus Ophiacantha, and all the affinities of the genus 

 Ophiocomina are with the genus Ophiocoma. 



The genus Ophiocomina as yet seems to be represented only by a 

 single species, O. nigra, which lives in the North Atlantic between the 

 coasts of Norway and the Azores and enters the Mediterranean. 

 Ophiocomina nigra, with its long divergent arm spines, has a general 

 appearance recalling very strongly that of Ophiacantha ~bidentata, 

 and it is certain that these two species have been very often confused. 

 This is evidently the reason why certain authors have mentioned 0. 

 nigra from the Arctic seas, from Spitzbergen and from the Barents 

 Sea, for example ; they refer in reality to Ophiacantha l>identata, for 

 O. nigra, an essentially boreal species, does not ascend to these very 

 high latitudes and does not appear to pass the latitude of Trond- 

 hjem or of Storeggen. 



Since I have had occasion here to speak of 0. nigra, I shall request 

 permission to add a few more words regarding the variations which 

 this species shows. 



First of all I may mention that besides 0. nigra two related forms 

 figure in zoological literature 0. raschi, described by G. O. Sars in 

 1872 from specimens from the coasts of Norway (Storeggen, 14G-183 

 meters [80-100 fathoms]) and O. tumida Miiller and Troschel, from 

 Genoa. 



Ophiocomina raschi is listed by Lyman in the Challenger report 

 ('82, p. 172) , but the reference which this author gives is incorrect, for 

 this species is not described in the Danish publication "Vid. selsk. 

 forh." (1872, p. 39), but in the Norwegian "Vid. selsk. forh." pub- 

 lished at Christiania in 1872, and the description is found on page 

 109. I do not believe that O. raschi should be maintained as a 

 distinct species; as Sars himself stated at the beginning of his de- 

 scription it does not differ from 0. nigra except in its larger size and 

 a different coloration ; " color disci et brachiorum laete ruber, 

 spinarum albidus," says the learned Norwegian naturalist, and he 

 gives for the dimensions, diameter of the disk 20 mm., length of the 



12 See Koehler, in Mortcnsen, Vidensk, Medd, fra Dansk naturh. Foren., K0benhavn, vol. 

 12, 1921, p. 53; Kcehler, Faune de Franco, Echinodermes, 1921, p. 93. 



