442 Miscellaneous. 
Notes on an Examination of four Species of Chitons, with Reference 
to Posterior Orifices. By Witttam H. Datu. 
1. Stimpsoniella Emersonit. 
Two specimens. 
The large and fine specimen from the Gulf of St. Lawrence pre- 
sented a posterior and terminal anus of large size, but with the edges 
not elevated into a papilla. The head of an ordinary pin could be 
inserted into it without violence. 
The orifices of the ovaries, bilaterally symmetrical, were situated 
just behind, and, as it were, under the shadow of, the last branchia on 
each side. There were two fenestra on each side of the anterior, a 
little further towards the girdle and a little larger than the posterior. 
This species resembles in most particulars the Symmetrogephyrus 
Pallasvi of Middendorff; and it would seem that his ungainly sub- 
generic or generic name should be adopted. The hairs are precisely 
similar in both species, as are the branchiz. The insertion-plates 
also agree, according to Dr. Carpenter, who examined a series from 
a specimen obtained by me in the Aleutian Islands. The principal 
differences, besides the larger size of S. Pallasvi, are as follows :—In 
the latter the hairs are more closely set, the texture of the epidermis 
is thicker and harder, the points of the valves are more nearly 
covered, and the skin is smoothly rounded over the back, not show- 
ing any thing of the form of the valves as is the case in S. Emersonit. 
I think also the valves are smaller, in proportion to the size of the 
animal, in Pallas than in Emersonii. 
2. Tonieclla marmorea, Fabr. 
This species showed a clearly defined posterior and terminal vent. 
The fenestrze of the ovaries were symmetrical on each side; but the 
branchiz pass behind them and conceal them. They are very small ; 
and I could not detect more than one on each side, though fresh spe- 
cimens, not hardened and contracted by alcohol, might show more. 
3. Trachydermon albus, Linn. 
The same remarks apply to this species. The vent was terminal, 
and on a papilla. 
4. Trachydermon ruber, Linn. 
Three specimens examined. 
These specimens were much hardened by alcohol. Removing the 
plates from above and then the inner lining membrane, beneath the 
large and well-filled ovaries the intestinal canal is seen, terminating 
in the median line posteriorly. From the outside the anus was not 
perceptible in the smaller specimens. By carefully turning back the 
outer edge of the girdle in the largest specimen, after removing the 
posterior plates, but without touching the animal with the dissecting- 
knife, the anus was perceptible, with a pellet of feeces impacted in 
the opening. It is very small, exactly in the median line behind, and 
not on a papilla. It is alsoa little higher up than in the other species. 
The “cancellated space” noticed by Mr. Emerton (as per notice in 
Ann. & Mag. Nat. Hist., March 1874, p. 121) on each side behind 
the branchie is a fold or groove containing the ovarian fenestre. 
‘There were in this specimen three fenestrae on each side ; but according 
