Hector. — On the Fossil Reptilia of Neio Zealand. 345 



peculiar character of the species. Ti-ansverse diameter of the centra 4 inches, 

 vertical diameter 3 -.5 inches, antei^o-posterior length 2 inches. The neural 

 spines are 1 -7 inches in antero-posterioi' width, 4-5 inches long, leaving only a 

 very narrow space between, and this is deeply notched by a bold zygapophysial 

 articulation 1-3 inches in depth. 



1^0. 5 h. — Is a slab with several vertebrse, and also obscui-e fragments of 

 the lower jaw, among which is a single tooth in sit-il (PL XXIV., fig. h). 

 This tooth is 2-2 inches long, and -3 inch in greatest diameter, which is at the 

 base of the crown, at 1 inch froia the tip. It is a curved, flattened, produced 

 cone, without any sign of a sharp ridge like that seen in the supposed tooth of 

 Mauisaurus, to which, however, the species has some affinity, but is easily 

 distinguished by the shorter vertebrse and the quadrate, not circular, form of 

 the articular facets. 



6. Plesiosaukus mackayii, n. sp. 



This species is not unlike the last described in the form of the tranverse 

 section of the centra of the vertebrae, but their length is very different, being 

 almost equal to the vertical diameter, as in Mauisaurus. But it is distin- 

 guished readily from that genus by the form of the humerus (6 a), which is dilated 

 at the distal end with a rounded articular extremity, and at the proximal end 

 is feeble. The shape is somewhat prismatic, but the bone has been a good 

 deal water-worn before being imbedded in the matrix. The clavicular bone 

 is slender, with a well-marked oblong articular surface. A fragment of the 

 coracoid bone shows this apparatus to have been very powerful, the width 

 being about 7 inches, with a very strong symphysial surface. The articular 

 surface at the angle of the bone for receiving the humerus is elongate and 

 narrow, being 1-7 inches wide at the middle, and tapering both ways, to a 

 length of 4 inches. The vertebral centra preserved, which belong to the 

 dorsal region, have the following dimensions : — Antero-posterior diameter 3 

 inches, transverse 4 inches, vertical 3-2 inches. The humerus measures 13 "5 

 inches in length, and is 8 inches wide at the dilated extremity. 



7. POLYCOTYLUS TENUIS, n. Sp. 



This genus, according to Professor Cope, has close affinities to Plesiosaurus., 

 but is distinguished by short deeply-concave vertebral centra, the concavity 

 not, however, being of an open conic form, as in Ichtliyosaurus, but distinctly 

 flattened at the fundus. The limb bones are remarkable for their size com- 

 pared with the vertebral column, indicating powerful natatory capacity. To 

 this genus, under the above specific name, I provisionally refer the speci- 

 mens marked 7 a, h, c, and d, all of which were obtained at the Amuri 

 Bhiflf. The first consists' of two slender paddle bones and one centrum, 

 probably cervical. The length of each paddle bone (humerus ?) is 9 inches, 



b2 



