150 PELTASTES 



B. Species from the Tipper Greensand. 

 Peltastes clathratus, Agassiz. PL XXXII, fig. 1 a—f, 2, 3, 4. 



Parkinson's Organic Remains, vol. iii, pi. i, fig. 13, 1811. 



Salenia clathrata, Agass. MSS. Morris's Catalogue of British Fossils, p. 58, 1843. 



— STELLULATA, Id. Ibid. Ibid. 



— UMBRELLA, Id. Ibid. Ibid. 



— OENATA, Id. Ibid. Ibid. 



— CLATHRATA, Bronti. Index Palseontologicus, p. 1007, 1849. 



UMBRELLA, Id. Ibid., p. 1008. 



— CLATHRATA, Forbes. In Morris's Catalogue of British Fossils, 2nd ed., 



p. 89, 1854. 



— STELLULATA, Id. Ibid. Ibid. 



— UMBRELLA, Id. Ibid. Ibid. 



— CLATHRATA, Woodward. Mem. of Geol. Survey, App. to Decade V, 



p. 6, 1856, 



— — Desor. Synopsis des Echinides Fossiles, p. 151, 1856. 

 Peltastes clathratus, Cotteau. Faleontologie Fran9ai8e, terr. Cretace, tome vii, 



p. 119, pi. 1028, fig. 8—18, 1862. 



Diagnosis. — Test siibglobose very convex above, poriferous zones straight, ambulacra 

 narrow, straight, with two rows of mammillated granules. Inter-ambulacra wide, three 

 pairs of prominent tubercles, miliaiy zone narrow. Apical disc very large, covering nearly 

 the entire upper surface, its outline very deeply indented between the ovarial and ocular 

 plates, which are smooth, and deeply notched at the sutures ; those connecting the centres 

 of the plates forming a distinct pentagon, each of the ovarial pores is the centre of five 

 radiating grooves with angular depressions between them. 



Dimensions. — Height nine twentieths of an inch ; six tenths of an inch. 



Description. — This Salenia is a very common species in the Upper Greensand of 

 Wiltshire, where it is often found in a fine state of preservation. The test in general is 

 small and subglobose, although depressed varieties sometimes occur. It is collected 

 likewise from the Grey Chalk near Folkestone, from whence the largest individuals have 

 been obtained. In the subglobose forms the upper surface is convex and inflated, and 

 the under surface is flat, with rounded sides (PL XXXII, fig. 1 a). The ambulacral 

 areas are narrow and very slightly flexed; two rows of small mammillated tubercles, 

 fourteen to sixteen in each, set closely together, are placed on the sides of the area (fig. 

 1 d), and a line of microscopic granules occupies the centre, and a few are scattered 

 between the tubercles (fig. 1 e). The poriferous zones are slightly flexed (fig. 1 d), and 

 the holes lie in oblique pairs (fig. 1 e) ; the septum separating each pair has a prominent 

 elevation ; and there are eight [)airs of holes opposite the larger plates. 



The inter-ambulacral areas are wide, and the plates in the cohimns unequal in size ; 



