408 



MR. G. S. BRADY'S MONOGRAPH OF 



16. Cythere concinna, Jones. (Plate XXVI. figs. 28-33, and Plate XXXVIII. fig. 7.) 



Cythere concinna, Jones, Tert. Entom. p. 29, pi. iv. figs. 1 a-lf. 

 Cythereis clavata, Sars, loc. cit. p. 39. 



Scandinavian type. Distribution : Recent — Great Britain, Norway. Fossil — Crag, England ; glacial 

 clays and raised beaches, Scotland, Ireland, and Norway. 



Valves, as seen from the side, ol)long, quadrangular, higher in front than behind ; 

 length equal to twice the height. Anterior extremity rounded, posterior rectangularly 

 or obliquely truncate, and slightly sinuated. Ventral margin nearly straight; dorsal 

 sloping in a right line, or gently arched, highest over the anterior hinge. Outline, as 

 seen from above, oblong quadrangular, twice and a half as long as broad, with nearly 

 parallel, sinuous sides, and broadly rounded extremities; the hinge-margins rather 

 depressed behind the middle. Anterior and inferior surfaces longitudinally furrowed. 

 The surface of the shell is marked (in highly sculptured specimens) with thickly set 

 small punctations, and on the posterior half with a network of fine ribs ; but very 

 commonly the surface is only slightly and irregularly undulated, bearing a few short 

 scattered setae — or sometimes roughened and studded with a few small tubercles, as 

 shown in fig. 32. Within, and parallel to, the anterior and ventral margins runs an 

 elevated ridge ; and there are also, in most cases, two shorter oblique ridges on the 

 posterior portion of the valve, a well-marked rounded tubercle in front of the middle, and 

 another over the anterior hinge. The hinge-processes are well-developed, the posterior 

 being placed very far back at the extreme dorsal angle. Colour yellowish. Last joint 

 of the upper antennae elongated, much longer than the preceding. Second joint of the 

 last pair of feet about equal in length to the united lengths of the third and fourth 

 joints ; terminal claw exceedingly slender, almost setiform. Terminal claw of first foot 

 pectinate. 



Length -^g in., height ^ in. , . if^-^^wv. 



Hub. The Minch and Hebrides, 45-60 fathoms (Mr. J. G. Jeffreys) ; Orkney {Mr. C. W. Peach) ; dredged 

 in 6-10 fathoms, Campbeltown Bay, Argyleshire, and Ormeshead [Mr. D. Robertson) ; off Scar- 

 borough (Mr. Leckenby) ; off Lewis, N.B., 59^ fathoms {Admiralty Soundings) ; Roundstone 

 (Dr. Alcock) . 



The sculpturing of the valves in this species is variable. The specimen from which 

 figs. 28-31 were drawn represents the best developed condition of surface-marking ; the 

 ribs and tubercles are often much less conspicuous. Possil specimens described by Prof. 

 T. Rupert Jones are very slightly sculptured, a condition shown in fig. 32 ; those found 

 in the Scottish glacial clay by Messrs. Robertson and Crosskey are often strongly marked 

 in the coarser surface-characters, but, in most cases, have comparatively little of the 

 delicate ribbing and punctation seen in some recent specimens. This, however, is one of 

 the most abundant of the Scotch Glacial Entomostraca, and shows a great range of 

 variation. Recent specimens dredged by Mr. Jeffreys in the Minch and the Sound of 

 Skye, at a depth of about 60 fathoms, also vary considerably, and are identical in 

 appearance with the majority of the fossil specimens. Those dredged further south by 

 Mr. Robertson, in shallower water, are usually more highly ornamented (figs. 28-31), 

 and are less frequently met with, in a fossil state. Por more copious illustrations of the 



