170 



' hyosternal,' ' hyposternal ' and ' xiphisternal,' as they succeed each other from before back- 

 wards. 



The scapular and pelvic arches, and the bones of the extremities, are described and figured 

 in the ' Ossemens Fossiles ' of Cuvier. 



Hunterian. 



770. The carapace of the green Turtle (Chelone my das). 



The first and last three ' neural ' plates are not attached to any vertebral elements. The 

 pleurapophyses of the first dorsal vertebra are short, expanded at their extremities, and arti- 

 culated there with the second pair of ribs, which are connate with the first pair of the costal 

 plates of the carapace, beyond which the rib extends in its ordinary slender form. The head 

 of the rib articulates by an extensive sutural surface to the sides of the contiguous extremi- 

 ties of its own centrum, and that of the vertebra in advance. The ninth pair of ribs resume 

 their connection exclusively with their proper centrum ; they are connate with the last pair 

 of costal plates of the carapace. The tenth dorsal vertebra has a pair of short and straight 

 pleurapophyses, which articulate by slightly expanded extremities to those of the preceding 

 vertebra. The pleurapophyses of the three following vertebrae articulate together at their ex- 

 tremities, against which the iliac bones abut ; these may be regarded, therefore, as sacral ver- 

 tebrae. The first three caudal vertebrae are likewise here preserved ; together with the mar- 

 ginal pieces of the carapace, and the dermal scutes which cover the exterior of the carapace. 



Mm. Brit. 



771. The carapace of a large Turtle (Chelone}, constructed as in the preceding spe- 

 cimen. The bodies of the fifth to the eighth dorsal vertebrae are wanting, or 

 mutilated. Hunterian. 



772. The osseous parts of the plastron of a Turtle (Chelone my das). The special 



names given to the nine portions by Geoffrey St. Hilaire are written on them. 

 In General Homology the lateral or parial pieces are expanded haemapophyses, 

 and the median piece a haemal spine. Hunterian. 



773. The skeleton of a small Turtle (Chelone my das). Mus. Langstaff. 



774. The skull of a green Turtle (Chelone my das). 



The expanded overarching part of the frontal and parietal bones is cut through and arti- 

 culated on one side, so that it may be removed to show the true parietes of the cranial cavity 

 which it conceals, and to which it affords additional protection. This modification seems to 

 relate to the proportional size of the head in this and other species of marine Turtles being 

 such as to prevent its retraction within the carapace. The numbers on the different bones 

 correspond with those in the Table of SYNONYMS. 



Presented by Prof. Owen, F.R.S. 



