1 92 Prof. T. R. Jones on the 



Nat. Hist, for October 1886, p. 266, pl.ix. fig. 12), in general 

 appearance ; but they are not identical with it. 



f Vine Coll. no. xiii. Bed no. 38. Buildwaa 



rp 1 i Beds. 



^^.^'""^ ^ LIY4 (fig. 14) ■) Bed no. 37. 



epecimens : ^^^.^ ^^^^ g^ j- g^ii^i.^.j^g gg^jg^ 



L 



LXiVs, 9. Buildwas Beds. 



V. Cytiieeella, Jones and Bosquet, 1849. 

 Ci/there, Cytherina, Cytherella, &c., auctorum. 



In the ' Monograph on Carboniferous Entomostraca,' 

 Palasont. Soc. 1884, bj Jones, Kirkby, and Brady, the 

 synonyms of the genus are given in full, and the characters 

 and distribution of the many known species (both fossil and 

 recent) are dealt with. 



Carapace oblong or subovate, rarely elongate, compressed, 

 especially in front ; valves thick and unequal, the right beitig 

 much the larger and overlapping the left all round, the two 

 edges being rabbeted together. Surface often smooth, but 

 sometimes pitted, reticulated, or striated. Muscle-spot indi- 

 cated by a roundish depression near the centre of the valve 

 externally and by a corresponding thickening within. 



1. Cytherella Smi'thii, sp. nov. 



(PI. Vli. figs. 15«, 15^, 16 a, 16^>.) 



Length. Height. Thickness. 



-r> ,. ( Fig. 16 : 12 6^ 5 



Proport,ons:|j,j| j,^^ 11 6 5 



Two specimens measured in lOOOths of an inch : — 



24 14 



22 12 10 



The little specimens before me belong to the group having 

 smooth valves, subovate or suboblong in outline, and with 

 a more or less cuneiform contour (edge view). Some speci- 

 mens have the usual central pit on the outside of the valves ; 

 some are also constricted across the middle of the smaller 

 valve, and these are narrower (lower) posteriorly than most 

 of the others, with a variable median convexity. May be 

 these are varietal or sexual differences. 



Narrow as the limits of difference seem to be at first 

 sight among the very many almost similar forms of Cythe- 

 rella, yet the diflerent proportions of length, breadth, and 

 thickness, with small variations of outline, constitute recog- 

 nizable distinctions among even the smooth forms. On such 



{: 



