412 



MONOGRAPH OF 



valve. Outline, as seen from above, compressed, sub quadrangular, width equal to one- 

 third of the length ; sides parallel, anterior extremity narrowed, truncate ; posterior 

 broader, slightly rounded. Surface of the shell covered behind the middle with closely 

 set circular pits. Colour yellowish. Animal unknown. 



Length -4V in. 



Huh. Birterlmy Bay, dredged (G. S. B.); Roundstone, in shell-sand (Dr. Alcock). 



The valves represented at figs. 36 and 37 belong apparently to the young of this 

 species, are slightly sulcate across the middle, and exhibit the semipunctate character of 

 the species very plainly. Several examples of single valves occurred in Dr. Alcock's 

 hell-sand, but only one perfect carapace in my dredgings from the same locality. 



22. Cvtiieee Jeffreysii, n. sp. (Plate XXIX. figs. 51-55.) 



Ulantic type? Distribution : Recent — Great Britain and Ireland. Fossil — Raised beaches, Scotland. 



Carapace, as seen from the side, ovate, highest near the front ; surrounded by a well- 

 veloped fillet or flange; height equal to more than half the length. The anterior 

 margin is wide, well-rounded, and bordered by a flattened lamina which is marked with 

 transverse hair-like lines. Posterior extremity narrowed and produced below into a 

 spinous plate. Dorsal margin highest over the anterior hinge-joint, where it bears a 

 conspicuous polished tubercle ; ventral margin nearly straight. Seen from above, the 

 outline is tumid, oblong, with nearly parallel sides, and tapering suddenly to the broadly 

 keeled extremities; the anterior hinge-tubercles very conspicuous. End view tumid, 

 broadly rounded below, narrowed above. Surface smooth and polished, marked with a 

 reticulated moniliform pattern, which is composed of rows of numerous small tubercles 

 (fig. 55). Animal unknown. 



Length ■£$ in., height -^ in. 



Hub 



(Dr. Alcock). 



(Mr. Jeffreys's dredgings) ; Roundstone, in shell-sand 



■ 



A form described by me in the ' Transactions of the Zoological Society ' (vol. v. p. 374) 

 under the name Cythere catenata is closely similar to the present in its surface-markings ; 

 and I hare since learnt that it is only the young of C. echinata, Sars, a species till recently 

 quite unknown to me, its catenate tubercles being developed in later life into spines. 

 It is possible that C. Jeffreysii may in like manner prove to be an imperfectly developed 

 form of some strongly spinous species ; but it has every appearance of mature growth, 

 and the specimens from both the above-named localities are in every respect similar. 



23. Cythere laticarina, n. sp. (Plate XXXI. figs. 1-4.) 



British type? Distribution : iW-Great Britain. 2W-R a i se d beaehes, Scotland. 



Carapace, as seen from the side, subtriangular, highest in front; length to height as 

 five to three. Anterior margin broad, rather suddenly rounded below, more gradually 

 above, bordered below by a row of short spines ; posterior margin rather angular. Dorsum 

 nest oj t the anterior hinge, whence it slopes gently and almost in a risht line back- 



ards 



Ventral margin nearly straight. The outline 





as seen from above, is obkm- 



