some species of Thyone and Cucumaria, in Anaperus, Orcula, 

 Colochirus, and Cuvieria. 



The species appears to inhabit muddy bottoms in shallow 

 water, among the roots of Zostera. It is undoubtedly the one 

 mentioned by Dr. Gould in his report on the Invertebrata of 

 Massachusetts, and as the Cabinet of the Society contains a 

 specimen from South Carolina, presented by Prof. Agassiz, the 

 Briareus probably exists on almost all portions of our coast. 

 It is commonly of a blackish brown color, and as the tentacula 

 are retracted when the animal is taken from the water, a 

 remarkable resemblance in form to some Ascidians is noticed. 

 They are found three inches long when contracted, and can 

 extend more than twice that length ; breadth exceeding half the 

 length in contraction. The ten tentacula, very much ramified, 

 supported by the solid tubes, and the oral circle, consisting of 

 one piece instead often as usual, are striking peculiarities. The 

 calcareous supports of the suckers are a terminal perforated 

 plate, the kalksiycken of Duben and Koran, and very numerous 

 lateral plates, slender, with a crested arch rising from their 

 centre. Five calcareous points of support are imbedded around 

 the anal aperture. The other points of distinction are sufficiently 

 expressed in the generic description. 



Mr. Ayres exhibited drawings showing the structure of 

 the species. 



Dr. T. M. Brewer read a paper giving a comparison of 

 the eg^ of the European and American Fork-tailed Petrel, 

 Thalassidroma Leachii, by which he had been led to the 

 conclusion that they are the same species. The paper also 

 contained descriptions of the egg of Bulvver's Petrel, Pro- 

 ceUaria Bulwerii, Dusky Petrel, P. obscura, and the Greater 

 Shearwater, Pujfinus major. The paper was referred to the 

 Publishing Committee. 



Mr. William Stimpson read descriptions of two new 

 species of shells from Massachusetts Bay, namely : Spinalis 

 Gouldii, and Thracia Couthouyi, and a Holothuria, under 

 the name of Anaperus unisemita. 



