442 ^fisreI/(n^fOKs. 



Notfs oil an KvamiiUitlon of four Species of Chifous, with liefit'encf 

 to Posterior Ori/ii-es. By Wilmam H. Dali,. 



1 . Stimpsoiiiella Einersotiii. 



Two spocimens. 



The large and tine specimen from tlif (iulf of St. Lawrence pre- 

 sentoil a posterior and terminal anus of large size, bnt with the edges 

 not elevated into a jiapilla. The he id of an ordinary pin could be 

 inserted into it witliout violenee. 



The oritiees of the ovaries, bilaterally symmetrical, were situated 

 jnst behind, and, as it were, under tlie shadow of, the last branchia on 

 each side. There were two fenestiieon each side of the anterior, a 

 little further towards the girdle and a little larger than the posterior. 



This species resembles in most paiticulars the Si/Dntiftroijephifrut; 

 PaUitxii of Middeudorff ; and it would seem that his ungaiidy sub- 

 generic or generic name should be adopted. The hairs are precisely 

 similar in both species, as are the branchiir. The insertion-plates 

 also agree, according to Dr. Carjienter, who examined a series from 

 a specimen obtained by mo in the Aleutian Islands. The principal 

 differences, besides the larger size of<$. P<tllasii, 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. Ememonii. 

 I think also the valves are smaller, in proportion to the size of the 

 animal, in Pallasii than in Emersonii. 



2. TonicAla marmorea, Fabr. 

 This species showed a clearly defined posterior and terminal vent. 

 The fenestras of the ovaries were symmetrical on each side ; but the 

 branchite pass behind them and conceal them. They are very small ; 

 and I could not detect more than one on each side, tliough fresh spe- 

 cimens, not hardened and contracted by alcohol, might show more. 



3. Trachydermon albiis, Linn. 



The same remarks apply to this species. The vent was terminal, 

 and on a papilla. 



4. Trachydennon ruher, Linn. 



Three specimens examined. 



These specimens were much hardened by alcohol. Remonng 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 di.ssecting- 

 knife, the anus was perceptible, with a pellet of faeces impacted in 

 the opening. It is very small, exactly in the median line behind, and 

 not on a papilla. It is also a 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 branchitc is a fold or groove containing the ovarian fenestrir. 

 Th« re were in this specimen three feneslrjp on each side ; liut according 



