CYTHERE. 



143 



is found in estuarine situations where the water is only slightly salt, as well as in the 

 littoral, laminarian, and coralline zones. 



Distribution. Recent. — Norway, Great Britain, Ireland, Holland, Mediterranean, 

 Gulf of St. Lawrence. 



Fossil. — Common in many of the Scottish beds. Ireland : AVoodburn, Belfast New 

 Docks, Raised beach, Portrush. Norway : Post-tertiary beds. 



.2. Cythere castanea, G. 0. Sars. Plate XITI, figs. 8 — 11, and Plate III, fig. 25. 



1865. Cythere castanea, G. O. Sars. Oversigtaf Norges marine O.^tracoder, p. 32. 



1868. — — Bradi/. Monog. Rec. Brit. O.-^tr., p. 398, pi. xxviii, 



fig. 27, and pi. xxxviii, fig. 6. 



1869. — — B. & R. Ann. and Mag. Nat. Hist., ser. 4, vol. iii, 



pi. xix, figs. 1 5 — 18. 



Carapace of the female, as seen from the side, oblong, subquadrangular, rather higher 

 in front than behind ; height equal to half the length ; anterior extremity obliquely 

 rounded ; posterior rectangularly subtruncate ; superior margin sinuous, sloping gently 

 backwards from the anterior third where it is highest, and terminating behind in an 

 obtuse angle; inferior sinuated in the middle and upcurved towards the extremity. Seen 

 from above, ovate, acuminate in front, rounded behind, sides subparallel and more or less 

 distinctly constricted in front of the middle. The shell of the male is more compressed 

 and when seen laterally is much more tapered behind, the supero-posteal angle more pro- 

 nounced, the infero-posteal entirely rounded ofi" ; superior margin quite straight and sloping 

 rather steeply backwards. Shell-surface closely set with small rounded pittings, and 

 marked usually with two curved transverse furrows ; colour reddish brown. 

 Length, 4-2-nd of an inch. 



Distribution. Recent. — Great Britain, Ireland, Norway, Plolland. 



Fossil. — Scotland: Tangyburn, Duntroon, Kilchattan, Dipple, Cumbrae, Dumbarton, 

 Paisley, Dalmuir, Oldniains, Govaii, West Tarbert, Oban. South Wales : Cardiff' New 

 Dock Basin. 



Very closely allied to this species are C. pellucida, porcellanea, Macallana, and tenera. 

 Prom the first named C. castanea may be distinguished by its usually darker colour, its 

 more closely punctate shell, the pittings of which are always small and round (not oblong or 

 of any considerable size), by the almost cuneate form of the male, and its perfectly straight 

 dorsal margin. C. tenera\& smaller, has no transverse furrow, is more finely, or not at all, 

 punctured, and is also sparingly papillose. C. porcellanea is more flexuous or reniform in 

 outline, smooth or indistinctly sculptured ; regularly ovate when seen from above, and 

 has a much less pronounced supero-posteal angle. The same remarks apply to C. Macal- 



