OF THE AJSTTWERP CRAG. 395 



Ctthere muceonata, Sars. (Plate LXVII. figs. 3 a-3 d.) 



Cythere mucronata, G. O. Sars, Oversigt af Norges Marine Ostrac. p. 48. 



Cythere spinosissima, Brady, Trans. Zool. Soc. (1865), vol. v. p. 386, pi. Ix. figs. 10 a-e. 



Carapace, as seen from the side, subquadrangular, of nearly equal height throughout, 

 height equal to fully half the length ; extremities rounded ; superior and inferior 

 margins nearly parallel ; the entire circumference (except the upper half of the anterior 

 margin) beset with blunt squamous spines, which are often dilated at the free extre- 

 mity, those of the postero-inferior angle being very long. Seen from above, the outline 

 is rhomboidal, much broken up with spinous projections. The sides of the valves are 

 beset with flattened squamous spines, often so much dilated at the end as to become 

 quite fan-shaped. End view hatchet-shaped. Length -^ inch (1-3 millim.). 



The spinous armature of this fine species is subject to great variation in the extent 

 of its development, the figures given in PL LXVII. exhibiting the most extreme form 

 with which I am acquainted ; it is found in the living state ofi' the coasts of Norway. 



The fossil specimens occurred in the " Sables moyens," zone a Bryozoaires. 



Ctthere joxesii (Baird). (Plate LXVII. figs. 2 a-2 d.) 



Cythereis jonesii, Baii'd, Brit. Entom. p. 175, pi. xx. fig. 1 (]850) ; Norman, Nat.-Hist. Trans. 



Northumberland and Durham, vol. i. p. 21, pi. vii. figs. 5-8 (1865) . 

 Cythere ceratoptera, Bosquet, Entom. foss. teiT. Tert. France, &c. (1852), p. 114, pi. vi. fig. 2. 

 Cythereis ceratoptera, Jones, Monog. Tert. Entom. Eug. p. 39, pi. iv. fig. 1 (1856). 

 ? Cythereis cornuta, Jones, Entom. Tert. Form. Eng. p. 39, pi. iv. fig. 19. 

 Cythereis fimbriata, Norman, Ann. & Mag. Nat. Hist. ser. 3, vol. ix. pi. iii. fig. 9 (1862). 

 Cythereis spectabilis, Sars, Oversigt af Norges marine Ostrac. p. 46. 

 Cythere jonesii, Brady, Monog. Recent Brit. Ostrac. p. 418, pi. xxx. figs. 13-16 (1865) ; Brady, 



Crosskey, and Robertson, Monog. Post-tert. Entom. Scotland, &c., p. 171, pi. xii. figs. 4-7. 



Carapace, as seen from the side, oblong subovate, higher in front than behind ; height 

 equal to more than half the length ; anterior extremity rounded, fringed with blunt 

 spines ; posterior also rounded, bearing a smaller number (about 5) of longer spines ; 

 dorsal and ventral margins nearly parallel and much broken up into irregular spines ; 

 over the anterior hinge is one very large and strong spine. Outline, as seen from above, 

 rhomboidal, greatest width behind the middle and equal to about two thirds of the 

 length. End view triangular. The surface of the valves, except along the margins, is 

 smooth and gently undulated ; there is a distinct elevated and rounded ridge just within 

 the anterior and posterior extremities ; and the general suiiace of the valves suddenly sinks 

 to a lower plane at a little distance behind the middle. Length -^ inch (1-1 millim.). 



I was at one time disposed to think that the form described by M. Bosquet as C. cera- 

 toptera might well be kept apart as a distinct variety of C. jonesii ; but, after exami- 

 nation of a large number of recent and fossil specimens, I now believe that there is no 

 character suiBciently persistent to warrant even this separation, the chief variations 



VOL. X. — PART VIII. No. 3. — August \st, 1878. 3 a 



