PLEISTOCENE FOSSILS. 261 



longitudinal section through the body of the worm, and shows nothing 

 of its external characters, and the somites of the body are indicated 

 only by the tufts of brown bristles or setae at intervals along the sides. 

 In the best specimen these are in the middle portion of the body, from 

 a tenth to a twelfth of an inch apart. On the anterior segments they 

 are closer together, the body having apparently been contracted in that 

 part. Each foot, as indicated by the setse — the soft parts having 

 entirely perished — seems to have had one strong spine and several 

 others, very fine and hair-like, in a separate bundle. When disengaged 

 from the matrix (which can easily be done by treating a small portion 

 with diluted acid) and examined microscopically, they seem to be 

 simple, nearly straight and pointed. Near what seems to be the ante- 

 rior extremity are obscure indications of one of the horny mandibles. 

 These characters, as far as they go, would indicate a chaetopod worm or 

 "sea centipede," and, of the species known to me on our coasts, they 

 resemble most closely that above named, which seems to be the iV. caeca 

 of Fabricius, and is a common and widely distributed species in the 

 North Atlantic and Arctic seas. 



PROVINCE ARTHROPODA. 

 Glass IV. — Crustacea. 



The most abundant species are bivalve Entomostraca, 

 which occur in great numbers in the Leda clay, associated 

 with Foraminifera. The species in my collection have 

 been kindly determined by Mr. J. S. Brady, who enumerates 

 the following : — 



Cythere MacChesneyi, nov. sp. 

 " Dawsoni (Brady). 

 - *' glohulifera (Brady). 

 '* Logani, nov. sp. 

 Gytheridea papulosa (Bosquet). 

 " punctillata (Brady). 

 " Sorbyana (Jones). 



** Mullen. 

 Cytherura Bobertsoni (Brady). 

 Cytheropteron complanatum, nov. sp. 



" inflatum (B., C, and R., MS.) 



" angulatum (B., C, and R., MS.) 



Eucythere argua. 



