THE BRITISH SECOJJ^DAEY EOCKS. o3 



Locality. The Haldon Greensand (N'eocomian). Original in the 

 British Museum. 



Remarhs. The ventral surface (PI. Y. fig. 5, a) of this elegant little 

 species has some resemblance both in shape and in appearance to 

 that of Ant. essenetisis, Schliiter, from the later " Cenomanien." The 

 radial pits, however, are relatively smaller and less distinctly four- 

 sided than in Ant. essenensis, and the cirrhus-sockets are considerably 

 more numerous and more closely set. 



6. AcTiNOMETRA ABNOEMis, n. sp. Plate Y. fig. 8. 



The centrodorsal of this peculiar little species is a thin, irregularly 

 four-sided plate with rounded angles. Its dorsal surface has gently 

 sloping sides, which bear about thirty rather deep cirrhus-sockets 

 in an incomplete double row. Inside the line of sockets the sur- 

 face is tolerably flat till near the centre, where it rises slightly. On 

 the slope of this central elevation are five somewhat lancet-shaped 

 pits, radial in position and rather variable in size and depth ; three 

 of them are partially filled by small rod-like pieces all of different 

 lengths. At the apex of the specimen I found an irregular circular 

 pit nearly fiUed up by a small tubercle rising somewhat above its 

 edge. 



On carefully cleaning away under water with a camel's hair 

 brush the clayey material at the bottom of the internal cavity, I 

 found this tubercle to be the broken end of a tiny rounded rod. 

 This seems to have somehow found its way into the cavity of the 

 centrodorsal, and to have become fixed in its dorsal opening by the 

 hardening of the clayey matrix. The central cavity is rather deep, 

 with nearly vertical walls on which some of the internal openings 

 of the cirrhus- canals are just traceable. Its upper axial opening- 

 is irregularly hexagonal with rather rounded angles, the ventral 

 surface of the plate sloping very gradually from its circumference 

 towards the opening, near the margin of which the slope increases 

 a little. On this steeper part are five shallow radial pits of variable 

 shape : two are roughly quadrangular, each with a low radial bar 

 dividing it into two parts ; another is distinctly bifurcate, one 

 division being longer than the other ; while the two remaining pita 

 are rather indistinct, their distal ends not being very clearly separa- 

 ble from the irregular furrows in the outer parts of the radial areas. 

 The basal grooves, also rather indistinct, are narrow and pardUcl- 

 sided. 



Diameter 4*5 millims. 



Locality. The Bradford Clay, Cirencester. 



JRemarlcs. The discoidal shape of the centrodorsal and the limita- 

 tion of the cirrhi to its sloping sides are characteristic oi Actinometra. 

 The presence of radial pits is unusual, for I have not found them in 

 any recent species of the genus. 



The specimen was found by the late Dr. S. P. Woodward and 

 given by him to Dr. Wright of Cheltenham, who has kindly placed 

 it in my hands for description. 



