73 
whether it is possibly identical with any known species; but it is 
certain that it is not identical with Loxosomella antedonis , the 
species that I found attached to the cirri of Hathromethra pro- 
lixa . x ) 
During a visit to the Swedish Biological Station, Kristineberg, 
in the summer of 1918, with the object of studying the develop- 
ment of Antedon petasus (and other Echinoderms) I found one 
day on examining a lot of this Crinoid a most curious abnormal 
specimen having some of its oral pinnules developed into true 
arms. Realizing, of course, at once the unusual interest afforded 
by this specimen, I was anxious to have it preserved with the ut- 
most care in order that it might be possible to give a good photo- 
graphic figure of it. Through some unfortunate circumstances, which 
need not be specified, it happened, however, that this special care 
resulted in the specimen breaking several of the arms, curving up 
the rest. It is therefore out of question to give a photographic 
figure of it that would be of any use, and I must content myself 
with giving some detail figures of the peculiar armstructures to 
• illustrate the following description. 
The anterior and the left anterior arms are quite normal. On 
the right anterior radius the anterior arm has the first oral pinnule 
on both sides transformed (Fig. 6, f.); the pinnule of the inner 
side has only two side branches near the point — it can hardly 
be said that they represent true pinnules, it has much more the 
character of a simple branching —; the pinnule on the outer side 
has developed into a true arm, almost as large as the main arm. 
The four inner joints retain the character of pinnule joints; on the 
fifth is developed a pinnule, and from here the joints take on the 
character of true armjoints, carrying pinnules in the normal way. 
Only the inner part is preserved, the part from the 6th pinnule being 
lost. There are no syzygies on the preserved part. The two lower 
! ) Th. Mortensen. A new species of Entoprocta, Loxosomella antedonis, 
from North-East Greenland. Danmark-Exped. til Grønlands Nordøstkyst 
1906—1908. Bd. V. 8. (Medd. om Grønland. XLV. 1911). 
This species has recently been found to occur also on Heliometra 
glacialis (R. C. Os burn. Bryozoa of the Crocker Land Expedition. Bull- 
Amer. Mus. Nat. Hist. XLI. 1919. p. 606.) 
