24 CRETACEOUS ENTOMOSTRACA. 



earliest known Cythereis. See ' Proceed. Bath N. H. and Antiq. Field Club,' vol. 

 vi, 1888, p. 256, pi. iv, figs. 13 a—c. 



Localities. — GhalJc, Wbiteabbey (Antrim) and Kent ; GhalJc-marl, Didcot ; 

 Detritus, Charing; Greensand, Cambridge. 



4***. Cythereis oenatissima (Beuss), var. retictUata, nov. (vel ornatissim,a- 



reticulata). Plate I, figs. 67, 68, 77 ; Plate IV, figs. 9—12. 



PI. I, fig. 67. Length 72; height -4 mm. 



PI. I, fig. 68. „ 1-0; „ -55 „ 



PL I, fig. 77. „ -88 ; „ -52 „ 



PI. IV, fig. 9. „ -83; „ -43 „ 



PI. IV, fig. 10. „ I'O; ,, •6; thickness "6 mm. 



PI. I, fig. 68, has the general shape of G. ornatissima, with broad anterior 

 margin, ventral ridge, well- developed front hinge, central tubercle, and variable 

 medial lobe behind it, as well as a spinose condition of the front, back, and rear 

 margins. The surface, however, is not spinose, but strongly and subconcentrically 

 punctate. In one case the medial lobe shows a neat, linear series of granules 

 (PI. IV, figs. 10—12). 



PI. I, fig. 77, does not appear to be essentially different from the foregoing. 

 The dorsal edge is coarsely dentate, and the medial post-central lobe is 

 represented by one or two small tubercles. The punctationis stronger and neater 

 in the specimens from Dunstable (figs. 67, 68) than in that from Ireland (fig. 77). 



PI. I, fig. 67, left-hand valve of a reticulate Gythereis near ornatissima, is 

 contracted in height (breadth). The front marginal rim passes backward into a 

 thin oblique ventral ridge; a subcentral lobe and a trace of a small tubercle 

 behind it are visible. 



The ornament in these three forms (PL I, figs. 67, 68, and 77, and PL IV, 

 figs. 9 — 12) approaches that of Gythere Koninclciana and ornata, Bosquet (see ' Mem. 

 Comm. geol. Neerlande,' vol. ii, pp. 110, 113, pi. ix, figs. 7 and 8) ; and the specific 

 relationship is not distant. As the reticulate ornament is not foreign to, but is 

 present in G. ornatissima, and as these under notice do not lose the reticulation 

 by the overgrowth of its mesh- walls, we may regard this feature in these instances 

 as sufficiently persistent to be a varietal character, and we place them as the var. 



RETICULATA. 



Localities. — Chalk, Horstead, Gravesend, and Whiteabbey (Antrim); GhalJc-rock, 

 Dunstable and Luton ; Chalk-marl, Didcot ; Detritus, Charing ; Gault, Folkestone. 



