CYTHERELLA SUBRENIEORMIS. 47 



Otthehella muensteri, Reuss. Elbthalgeb., &c., pt. 2, 1874, p. 152, pi. xxviii, 



figs. 6 and 7. 

 — — Jones and Sherlorn. Suppl. Monogr. Tert. Entom., 1889, 



p. 47, pi. ii, fig. 10. 



Length '75; height '4; thickness '32 mm. 



In the ' Supplem. Monogr. Tert. Entom.,' 1889, an attempt was made to 

 classify such of the Gytherellse, as occur in the Tertiary formations of England 

 according to their shape, as to outline and the relative position of the greatest 

 thickness in the carapace. In this grouping Gytherella Muensteri comes with its 

 thickness at or near the hinder end, which in some cases, as in G. Beussii (op. cit., 

 PI. II, figs. 8 a, b), gives a thick and almost truncate end to the carapace, but not 

 so sudden as in the cuneiform edge views of some varieties of G. Beyrichi (op. cit., 

 PI. II, figs. 1 and 9), nor indeed as in Gytherella Muensteri of the Chalk. These 

 relative measurements were taken from perfect carapaces, but internal casts of the 

 same species, such as in the present Monograph, PI. Ill, fig. 65 (formerly 

 PI. VII, fig. 25 ft), has a different and more truncate aspect. There are many 

 specimens of G. Muensteri which are blunt posteriorly, but not actually truncate. 



M. Bosquet in 1852 explained his reasons for referring this species to 

 G. Muensteri (Romer). The coarse pitting of Romer's figure was regarded by 

 M. Bosquet as being represented by the exceedingly linear punctation that he saw 

 in his specimens from Maastricht. Our Cretaceous specimens are smooth. 



Localities. — Ghalk, Norwich, Horstead, Colchester, and South-east England ; 

 Ghalh-rock, Dunstable ; Ghalk-marl, Dover and Didcot ; Detritus, Charing ; GauU, 

 Folkestone, Leacon Hill, and Godstone ; Greensand, Cambridge. 



Foreign. — Maastricht, Balsberg (Sweden), &c. See also Reuss, 'Elbthalgeb.,' 

 pp. 152 and 154. 



4. Cytheeella subeenifoemis, sp. nov. Plate III, figs. 44 and 45. 



Length "85 ; height "45 ; thickness '3 mm. 



Subreniform, arched dorsally and slightly incurved ventrally; ends rounded, 

 the anterior more boldly than the other ; edge view long, narrow-oval, rather 

 blunter behind than in front ; end view oval. 



This Gytherella is nearly allied to several published forms, but matches none 

 exactly. If it were not arched on the back it would be very near to Reuss's 

 C. parallela, as figured by G. S. Brady, ' Trans. Zool. Soc.,' vol. x. In shape 

 also it somewhat resembles Romer's not very satisfactory figure of G. Muensteri, 

 but it is too hollow ventrally, too blunt posteriorly, and is not punctate. It is 

 very near G. pulchra, Brady, but too reniform in shape for that species. In 



