78 Miscellaneous. 
globular head. The ovaries resemble little bunches of grapes of an 
orange-colour, but each grain is formed by an egg, and not by a 
secretory czecum. 
The egg during its development projects out of the gland, and is 
suspended by a peduncle, which is very probably broken at the period 
of extrusion. 
On each side of the median line in the concave valve there is a 
glandular canal, with an internal and external orifice; this, which 
represents what Mr. Hancock calls the supposed auricles of the 
pseudo-hearts, is in relation to the ovary or testis, and serves, pro- 
bably, for the issue of the ova and seminal fluid. 
The young embryos of the Thecidia are suspended from two of 
the cirri of the arms—those of the middle behind the mouth. These 
cirri, which may be called suspensors, curve backwards and bury 
themselves in a median incubatory pouch, placed between the two 
ovaries. This peculiarity impresses upon the shell a character which 
enables us to distinguish the male from the female Thecidia, when 
the animal no longer exists. A small notch for the passage of the 
two embryoniferous cirri upon the external twisted lamella which 
supports the arms always indicates the female sex. There are few 
examples of this possibility of recognizing the sexes of shells. 
The entire series of the development of the ova could not be in- 
vestigated. The youngest embryos observed resembled an aggrega- 
tion of large cells. Starting from this state, in which the young 
animal is ovoid, three furrows are seen to be formed perpendicular 
to the principal axis, dividing the embryo into four lobes; the two 
median are comparatively very large, the two outer ones very 
small. One of the latter appears to be hollowed into a cavity like a 
sucker ; the other presents a longitudinal fissure surrounded by two 
or four red eye-like spots. It is very probable that this is the ante- 
rior extremity, and that its fissure becomes the mouth. The embryos 
move by the agency of the vibriatile cilia with which they are covered ; 
they often contract themselves. They appear to bend themselves 
upon the median furrow, and then the greater diameter is much 
diminished. The substance contained in the anterior median lobe 
breaks up into lobules, which will afterwards represent the ceca of 
the liver.—Comptes Rendus, November 11, 1861, p. 849. 
On a new Species of Neotoma (N. ferruginea) from Guatemala. 
By R. F. Tomes. 
The present species of Neotoma is so well-marked a species that 
it will be scarcely necessary to lengthen the description by comparing 
it with other species of the genus. 
It is typically a Neotoma, and in size about equals the Mus rattus 
of Europe. General form rat-like; the head rather elongate, and 
the muzzle somewhat pointed. Muffle small, being little more than 
a flat space between the nostrils, and with scarcely any part quite 
free from short, fine, scattered hairs. Upper lip cleft from the muffle 
downwards, and well covered with short hairs; nostrils rather small 
