212 CHEL0N1A. 



the 1st marginal bone articulates almost wholly with the 

 nuchal, whereas in the adult it has a long articulation 

 with the 1st costal. The relative shortness of the bridge 

 is indicated. The xiphiplastral is devoid of any facet 

 for articulation with the pubis. The great relative antero- 

 posterior diameter of the first pair of marginal shields 

 is very characteristic. 



Beclcles Collection. Purchased, 1877. 



48263. Slab showing the dorsal aspect of a similar but rather smaller 

 carapace ; from Durdlestone Bay. This specimen has been 

 somewhat crushed and the contour of the vertebral shields 

 is not clearly shown. The marginals are wanting and 

 the nuchal is imperfect ; the contour of the latter is, how- 

 ever, the same as in the preceding specimen. 



Becldes Collection. 



48353. Slab showing an imperfect shell agreeing precisely with No. 

 48262 ; from Durdlestone Bay. The dorsal aspect of the 

 greater part of the carapace is shown, but the nuchal is 

 wanting. The right humerus is seen on the left side of 

 the carapace. Bechles Collection. 



48354. Slab showing an imperfect shell of rather smaller size than 

 No. 48263 ; from Durdlestone Bay. The dorsal surface 

 of the imperfect carapace and the ventral aspect of the 

 plastron are exhibited. In the latter the mesoplastrals 

 terminate externally in a point. The scapulo-precoracoid 

 of one side is also shown. Beclcles Collection. 



48347. Slab exhibiting the ventral aspect of an imperfect plastron 

 agreeing approximately in size with No. 48262 ; from 

 Durdlestone Bay. The ento- and epiplastrals are wanting, 

 and the xiphiplastrals are imperfect. The bridge is rela- 

 tively much shorter than in adult specimens, its length 

 being only equal to half the inter-inguinal diameter of the 

 hypoplastrals. The mesoplastrals terminate externally in 

 a point, and apparently permitted the hyo- and hypoplas- 

 trals to come almost or quite into contact at their outer 

 extremities. Beclcles Collection. 



48343. Slab exhibiting the ventral surface of a somewhat smaller 

 imperfect plastron and other bones; from Durdlestone 

 Bay. The xiphiplastrals and the right hypoplastral are 

 imperfect. The mesoplastrals, although pointed externally, 



