MR. G. S. BRADY'S MONOGRAPH OF 



"■ular fossa? arranged in more or less distinct longitudinal rows, which are separated by 



arp rid£ 



Length 



Colour yellowish brow 



Animal unknown 



i 



5<> 



in. 



Fyne, Plymouth (Rev. A. M. Norman) 



Oban and Ormcshead (Mi 



Aberdeenshire (Mi 



Northumberland and 

 el Islands (Mr. J. G. 



Jeffrey*) ; De\ onshire coast (M. 



<*>. Cytheuopteron rectum, nov. sp. (See Appendix.) 



Genus 10. Eythocythere, G. 0. Sars. 



Valves subequal, smooth or very sparingly sculptured, almost destitute of hairs ; thin 

 and fragile. Hinge-joint quite simple or composed of a slight bar and furrow ; no teeth. 

 Upper antenna? elongated, seven-jointed ; the second joint large and thick and bearing a 

 seta on its anterior and posterior margins ; the other joints suddenly much narrower, 

 forming a long slender lash, which bears several seta?; penultimate joint linear and 

 destitute of seta?. Lower antennae tolerably robust, four-jointed; second joint large; 

 llagellum long, Inarticulate, its last joint long and setiform. Mandibles constricted above 

 the distal extremity, strongly toothed ; palp four-jointed, bearing a well-developed bran- 

 chial plate, which is set with numerous ciliated setae. Terminal lobes of the first pair of 

 jaws very short and thick; branchial plate large, ovate, bearing 



numerous marginal 



ciliated setae, and at the base four long and denexed simple setae. 



Feet 



elongated, 



terminal claw very long and slender, second and third joints bearing each a short apical 



seta ; basal joint of the first pair furnished at the base with a small lobe, which bears two 



very large and densely ciliated, and two smaller and simple setse. Abdomen ending in a 



very large and acuminated process ; postabdominal lobes narrow and bearing three hairs. 

 Eyes mostly absent. 



The species grouped under this genus present two very distinct types, so far as the 

 characters of the shell are concerned ; but according to the investigations of Herr G. 0. 

 Sars, the structure of the animal itself is the same in both types. My own observations 



specimens, and are necessarily 



altogether on dried 



of the animal have been made 



imperfect, but, so far as they go, they are quite in accordance with those of that most 

 accurate author. 



1; Bythocythere simplex (Norman). (Plate XXXIII. figs. 23-27, and Plate XL. fig. 8.) 



Cy there simplex, Norman, Nat. Hist. Trans. Northumb. & Durh. vol. i. p. 17, pi. v. figs. 1-4. 

 Jonesia simplex, Brady, Trans. Zool. Soc. Lond. vol. v. p. 363, pi. lvii. figs, lla-e. 

 Bythocythere acuminata, G. O. Sars, loc. cit. p. 86. 



Scandinavian type. Distribution : tecwi*— Baffin's Bay, Norway, Britain. l?W-Glacial, Scotland. 



Carapace of the female, as seen from the side, oblonj? fusiform, about twice and a half 



in the 



as long as broad, rounded in front, acuminate behind 



Dorsal margin straight 



middle, sloping suddenly downwards at the posterior extremity, gently rounded in front 



