6 FOSSIL REPTILIA OF THE 



obliquity as in fig. 2 ; and the surface of the bone between the right and left sockets 

 shows the same median longitudinal groove. Opposite the middle sockets the sides 

 of the jaw are preserved nearly to the median inferior ridge, as shown in fig. 7, c; 

 these sides being flat and straight, and giving the transverse section shown at fig. 7, d. 

 The intervals of the sockets are a little wider, proportionally, than in some of those in 

 fig. 2, but not more than a hinder position in the jaw would account for, without 

 having recourse to a distinction of species to explain it. 



Two species, however, are satisfactorily established, both of them distinct from any 

 of the known large Pterodactyles of the Chalk, by the portions of jaws from the Upper 

 Green-sand near Cambridge, viz., Pterodactylus Sedgwickii, with more approxi- 

 mated alveoli (Tab. I, figs. 1 and 2, with probably 6 and 7) ; and Pterodactylus 

 Fittoni (ib., figs. 3, 4, and 5). 



To which of these large species the teeth and bones next to be described belong is 

 not satisfactorily determinable, but indications of their appertaining to more than one 

 such species now and then occur with more or less significancy. 



Teeth. 



Various teeth, but few quite entire, have been rescued by the care and perseverance 

 of Mr. Lucas Barrett from the rubbish of fragmentary fossils accumulated during the 

 diggings for phosphatic nodules in the Green-sand deposits near Cambridge. Guided 

 by the proportions of length to breadth, by the elliptic section, and the concordance of 

 the minute markings on the crown and base with those on the portions of teeth, as in 

 Tab. I, fig. 2, d, and 6, b, remaining in the jaws of Pterodactylus Sedgwickii, many of 

 the above detached teeth can be satisfactorily referred to the genus, if not to that par- 

 ticular species. 



The base or implanted part of one of the largest of these teeth is figured of the 

 natural size in Tab. I, fig. 10. It has belonged to a Pterodactyle as large as that 

 represented by the fragment of jaw (fig. 6), if not to the same individual ; it presents 

 the same eUiptical transverse section as the implanted base of the tooth in fig. G, b ; 

 shows a widely excavated pulp-cavity at the base, and gradually tapers to the crown ; 

 the cement, about gd of a line in thickness, is roughened by longitudinal grooves, not 

 continuous for any great length, but uniting, or bifurcating, in an irregular reticulate 

 pattern, forming long and very narrow meshes, the raised interspaces being equal 

 in breadth to the grooves. In a few teeth the base shows an oblique depression, 

 evidently due to the pressure of a successional tooth, as shown at Tab. I, fig. 8, o ; 

 in these the basal pulp-cavity is more or less filled up by ossification of the pulp. 

 The enamel of the crown seems smooth and polished, and, under the lens, shows only 

 extremely delicate, slightly and irregularly wavy, longitudinal, but often interrupted 

 or confluent, ridges. The crown is straight in a few teeth, as at Tab. I, fig. 9, but 



