454 



MR. G. S. BRADY'S MONOGRAPH OF 



than the three following; penultimate joint of the lower antennse very slender, and 

 twice as long as the preceding. Branchial appendage of the mandible bearing eight 

 backward-pointing setae. Second joint of the last pair of feet shorter than the two 

 following." 

 Length ^ in. 



Hah. Rare; in depths of 10-60 fathoms. Birterbuy Bay and coast of Northumberland off Holy Island 

 (G. S. B.) ; the Minch, and one dead shell in rock-pool, Herm {Rev. A. M, Norman). 



Genus 12. Cytherideis, Jones. 

 Carapace slender, elongate, subovate, tapering towards the front, not much compressed 

 laterally. Hinge-margins nearly simple ; shell smooth, finely punctate. The right valve 

 overlapping the left in the centre of the ventral aspect. Animal unknown. 



Cytherideis subulata, Brady. (Plate XXXV. figs. 43-46.) 

 ('ythere flavida, Baird, Brit. Entom. p. 168, t. xxi. figs. 12, 12 a. 



British type. Distribution : Recent — Britain, Ireland, Bay of Biscay, Cape Verd, Levant. Fossil — 

 Glacial, Scotland. 



Carapace, as seen from the side, much attenuated in front, highest behind ; greatest 

 height equal to one-third of the length ; sharply rounded in front, broadly and obliquely 

 rounded behind. Superior margin sloping with a gentle curve from the middle forwards, 

 nearly straight behind the middle ; inferior margin gently sinuated in the middle. Seen 

 from above, the outline is compressed ovate, widest behind, tapering to an acute point 

 at each extremity ; greatest width equal to one-third of the length. Shell thin and fragile, 

 yellowish, marked with fine closely set impressed puncta ; the anterior and posterior 

 margins with transverse radiating lines ; centre of the valves obscurely sulcate trans- 

 versely. End view circular. Animal unknown. 



Length ^ in. 



Hab. In shell-sand from the Mumbles, Donegal Bay, and Roundstone (G. S. B.) ; Macduff and Peterhead 

 {Mr. D. Robertson) ; Channel Islands {Mr. J. G. Jeffreys) ; Devonshire coast {Mr. C. Spence Bate) ; 

 Frith of Clyde, Falmouth, and in rock-pools, Herm {Rev. A. M. Norman). 



All the examples of this species which I have seen are merely empty shells, and 

 therefore I cannot refer it with certainty to its proper position. The shell, though in its 

 lateral aspect very similar to some forms of Faradoxostoma, differs in some important 

 particulars : it is not laterally compressed as all the elongated forms of the latter genus 

 are ; the shell is more horny in character, and not smooth and polished. The lucid spots 

 are four, large, quadrangular, and irregularly grouped. Lastly, the overlapping ventral 

 margin of the right valve almost certainly proclaims that it cannot belong to that genus, 

 which always exhibits a longitudinal ajDcrture between the two contact-margins in front, 

 for the protrusion of the suctorial apparatus. Under these circumstances, I have 

 retained for this species the generic term Cytherideis, under which group, as originally 

 defined by Professor Bupert Jones, it would naturally fall. Miiller's Cythere Jlamda, 

 with which Dr. Baird identifies it, seems to me to belong to another species, probably 

 Paradoxostoma variabile. 



