KIMMERIDGIAN PTERODACTYLES. 545 



but sufficient remains to show its liemispheroid form, and the mere chink dividing it 

 from the radial condyle instead of the groove which is here seen in Birds. The flexor (?) 

 ridge, leading to the broken tuberosity, extends more forward than in Pterodacti/lus 

 Duncani (ib., fig. 13), and contributes to a deeper concavity above the condyles on the 

 thenal aspect of the distal expansion of the humerus. The transverse ridge behind the 

 condyles is confluent therewith at its extremities, the defining groove not being developed 

 (ib. ib., 16')- The broad shallow canal for the ' triceps' tendon marks the anconal surface 

 of this expansion (ib., fig. 16). 



To the same species of Pterodactyle may probably belong the proximal end of the 

 smaller example of the first phalanx of the fourth or wing-finger, of which I have given two 

 views in Plate 19, figs. 22, 23, and 23^ to contrast with those of the same bone and part 

 of Pterodactylus Manselii. The olecranoid process in Pterodadylus Pleydellii is relatively 

 longer and more incurved ; its apex is not truncate ; it is more compressed ; has a 

 smaller and lower posterior tuberosity, and a smaller basal tuberosity. The longer 

 concave articulation is similarly extended upon the anterior angle. From the tuberosity 

 at the corresponding or lower end of the shorter concavity a ridge is continued down 

 the bone, giving a triedral form to the shaft as far as it is preserved in this and the 

 previously described specimen (figs. 20, 21). The bony wall of the shaft is thin and 

 compact, the air-cavity large, and in one specimen occupied by crystallised calcite. 

 The two narrower sides are concave or flat transversely ; the broader side is gently 

 convex ; it shows, in both species (figs. 21, 23), a longitudinal linear impression, which 

 may indicate a confluent rudiment of a fifth digit. 



To the above-described, well-defined, trochlear or ginglymoid joint were adapted the 

 two obliquely disposed condyles of the distal end of the metacarpal of the fourth or 

 wing-finger. 



I have pleasure in contributing this mite of testimony to the unremitting attention to 

 the fossil evidences of Kimmeridgian Vertebrates, discovered from time to time on his 

 estates by John C. Mansel-Pleydell, Esq., F.G.S., of Longthorns, Blandford, and to the 

 wise liberality by which they have uniformly been deposited in the National Collection, 

 where inferences and conclusions from their study can be tested by Palseontologists. 



C. — Pterodadylus, sp. incert. 



Two specimens of the carjjal bone, provisionally referred in a preceding Section 

 to a Pterosaurian ' midforme' are figured in Plate 19, figs. 24 — 27. They were both 

 obtained from the " Kimmeridge Clay," at Weymouth, Dorsetshire. -t 



The distal surface of the smaller specimen is given in figure 24 ; they show the larger 

 concavity (a), and the smaller one (6), adapted to the two proximal condyles of the 



