310 
MISCELLANEOUS. 
Description of the Larva of a Brachiopod. 
By F. Miuuer. 
Dr. F. Mituer has sent from Brazil the description of a larva be- 
longing undouhtedly to a Brachiopod, which is the more interesting 
as the Brachiopoda are the only Mollusca regarding the development 
of which we have no information. 
The larva in question is a small, perfectly orbicular bivalve Mol- 
lusk. The two valves are similar, but unequal in size, the dorsal 
valve being the largest. At the place of the hinge a small oval plate 
is placed transversely between the two valves of the shell. The 
mantle is gaping all round. Five pairs of very stiff setee, of which 
one is much stronger than the others and curved backwards, project 
at the periphery. They originate in the mantle of the ventral half; 
at least, this is the case with four of them. A series of finer sete 
spring from the circumference of the mantle of the dorsal valve, 
and curve down upon the outside of the ventral valve. The animal, 
as well as the shell, would be divided into two perfectly symmetrical 
halves by a plane drawn vertically through the middle of the hinge. 
The body, which is furnished with an alimentary canal, two auditory 
capsules, and two eyes, fills the posterior half of the space between 
the valves. The anterior half is occupied by four pairs of cylindrical 
arms, between which a rounded knob is situated. Behind this knob 
the mouth is perceptible. These four pairs of arms are supported 
upon a common peduncle, at the extremity of which, therefore, the 
mouth is placed. The arms are covered with a very well developed 
ciliary coat, by the agency of which the little animal swims. The 
reproductive and circulatory organs are wanting. 
During natation, the mouth is always directed forwards, which is 
in favour of the generally received opinion as to the anterior and 
posterior regions in the Brachiopoda. It is, in fact, now evident that 
the Brachiopods are depressed animals, have an anterior or ventral 
and a posterior or dorsal valve. MM. Agassiz and Vogt are there- 
fore wrong in regarding them as compressed animals, like the Lamel- 
libranchiate Mollusks—that is to say, as animals having a right and 
a left valve. 
The larva, moreover, can not only swim, but also creep. This 
latter mode of progression is effected by a sort of rotation of the ven- 
tral valve alternately to the right and left. In this movement the 
animal pushes by supporting itself principally upon the strongest of 
the bristles above mentioned. — Reichert und Du Bois’ Archiv, 
1860, p. 72. 
