246 
in this abnormal appearance of pedicellariæ a case of atavism; the 
same maj perhaps be the case with the unusual length of the 
arms in this specimen, also the four normal arms heing conspicu- 
ouslj longer than normally in this species, which is otherwise 
nearlj pentagonal. — I was at first inclined to regard this remark¬ 
able specimen as a hybrid between Ceramaster granularis and 
Hippasteria phrygiana (Parel.) both of which are common in the 
Trondhjemfjord. The above explanation, however, appears to me 
more natural; the pedicellariæ are not like those of Hippasteria , 
and there are no other characters clearly recalling that species. 
In Ophiurids the only case of abnormally branching arms 
which I have found recorded is that of Ophiomusium impurum from 
Koehler, mentioned above. It appears that such abnormalities 
are comparatively much rarer in Ophiurids; the three cases, which 
I shall describe here, are then of some interest as a relatively 
very considerable addition to the knowledge of such monstrosities 
in this group of Echinoderms. 
In PI. IV. Pig. 5 is represented a specimen of Ophiura (Ophio- 
glypha) Sarsi Ltk. from West Greenland, taken in the Northern 
Strømfjord in 1911 by Dr. V. Nordmann, which shows the 
abnormalitv that one arm has been di vided from the base, the 
specimen having thus six arms. The inner armplates are very 
irregular, as are upon the whole the corresponding mouth edge 
and interambulacrum. The madreporite is not discernible, so that 
the serial number of the monstrous arm cannot be ascertained. 
A somewhat similar monstrosity is found in Ophioscolex pro - 
lifer Studer, the specimen described and figured by Studer 1 ) having 
a small arm protruding from the disk between two normal arms; 
it is, however, as appears from the figure 13c. of Studer’s 
memoir, not a branching of an arm, but a formation of a new arm 
x ) Th. Studer. Ubersicht fiber die Ophiuriden, welche wahrend d. 
Reise S. M. S. Gazelle um die Erde 1874—1876 gesammelt wurden. 
Abhandl. d. K. Preuss. Akad. d. Wiss. Berlin. 1882. p. 28. Taf. III, 
Fig. 13 a—e. 
