66 Reginald W. Hooley — A new Tortoise from Hordicell. 

 VI. — On a new Tortoise from the Lower Hbadon Beds of 



HORDWBLL, NlCOMIA HEADONENSIS, SP. NOV. 

 By Eegixald "W. Hooley, F.G.S. 



THE bones of the carapace and plastron from which this species 

 has been determined were discovered in a thin seam of grey 

 sand intercalated in the Mammalian band of the Lower Headon Beds 

 at Hordwell. Hampshire. They were lying scattered over an area 

 of about four feet. The broken edge of the entoplastral and right 

 hyoplastral were sticking out of the cliff face. The sea had carried 

 awav the missing portions of these bones and probably those lost of 

 the carapace and plastron. 



The illustration is from a photograph of an attempted restoration 

 in plaster. The discovered bones are shaded, and from these the 

 missing plates can easily be restored ; the portion of the carapace 

 anterior to the second neural is alone doubtful. 



Of the plastron the character of the hyoplastrals is of course clear, 

 and the remainder worked out from its nearest allies. The carapace, 

 were it not for its posterior broadening, would be very ovoid ; 

 indeed, the line of the costal and marginal suture is quite ovate. It 

 probably measured 19 mm. in length. It is well vaulted, with 

 a slight depression posteriorly where it becomes expanded. There 

 is no discernible carination, and the marginals are not serrated. 



Of the carapace, the bones found consist of the second, third, and 

 sixth neurals, and the right half of the second supra-pygal. The 

 proximal end of the second, the whole of the third, sixth, seventh, 

 and eighth costals of the right, a piece of the third, the entire fourth 

 and sixth, and the distal end of the seventh costal of the left. The 

 seventh, eighth, tenth, and eleventh marginals of the right, and 

 the fourth, fitth, sixth, eighth, ninth, and tenth of the left. Of 

 the plastron, the greater portion of the entoplastral, a small moiety 

 of the anterior end alone being destroyed. A part of the right 

 hyoplastral and the whole of the left. 



The neurals have their short sides placed posteriorly. The second 

 is octagonal and the third and sixth hexagonal, and judging from 

 the proximal ends of the neighbouring costals the fourth and fifth 

 are hexagonal and also symmetrical with the third and sixth. The 

 surfaces of the second neural sutures with the first costals are not 

 on a plane, but concave, the left showing a greater depression than 

 the right, but this is doubtless an individual trait. As evidenced 

 by the sulcus, the vertebral shields were hexagonal with a small 

 projection in the centre of the anterior margin. The posterior 

 border of the fifth slopes downwards to the sulcus on the eleventh 

 marginal, whence it apparentlj^ crosses the pygal on the same 

 horizon. The vertebrals are nearly as broad as long, but compared 

 with the costals narrow. The latter are much longer than broad. 

 The posterior marginals are slightly fluted parallel to their edge. 



The plastron is strongly united to the carapace by suture. On 

 the seventh marginal there is a very powerful inguinal buttress, 

 which from the prominence of its ridge at the marginal suture 



