100 
of this species. As pointed out by Matsumoto^) a main character 
of the Åstrochematinæ is the joining of the lateral plates in the 
ventral midline of the arm, in contradistinction to the Trichasterinæ, 
in which the lateral plates are separated by the ventral plates. Ac- 
cording to this character the present species is no Ophiocreas at 
all, but should be included in the subfamily Trichasterinæ, repre- 
senting a new genus, 
the nearest ally of which 
would appear to be Åstro- 
ceras. But then it differs 
from the Trichasterinæ 
in the lateral plates not 
projecting ventrally like 
hanging rods, which is 
also a character of the 
Trichasterinæ. Regarding 
the anatomical charac- 
ters pointed out by Ma t- 
sumoto as distinguish- 
ing the two said subfamilies, I have no material for examining 
them in the present species. The matter is rather puzzling, and as 
it would hardly be possible to reach a definite solution of the 
systematic problems raised by this form without going into a very 
detailed study of the whole family Trichasteridæ, for which I have 
neither material nor time, I shall provisionally leave the present 
species within the genus Ophiocreas, in spite of the marked diffe¬ 
rence in the lateral and ventral plates. 
Also Ophiocreas adhærens Studer has the sideplates separated 
by well developed ventral plates. This species, apparently, is closely 
related to O. constrictum; I should, indeed, not be surprised at all, 
if it ultimately turned out to be identical with that species. From 
the description given by Studer^) this would appear rather im- 
1) H. M at sum o to. A new classification of the Ophiuroidea; with descript- 
ions of new genera and species. Proc. Acad. Nat. Se. Philad. Vol. LXVII. 
1915 p. 51. 
2) Th. Studer. Verzeichniss d. wahrend d. Reise S. M. S. „Gazelle“ um 
die Erde 1874—76 gesammelten Asteriden und Euryaliden. Abh. d. Kgl. 
Preuss. Akad. d. Wiss. Berlin, a. d. Jahre 1884. 
Fig. 1. The ventral plates aiicl lateral plates of two 
consecutive armjoints of Ophiocreas longipes (1) and 
Ophiocreas constrictum (2). The small round spots on 
the outer end of the lateral plates indicate the grooves 
for the insertion of the armspines. ®/i. 
