PACHYRHIZODUS. 129 



4. Pachyrhizodus subulidens (Owen). Plate XXVII ; Text-figure 39. 



1842. Raphiosaurus subulidens, R. Owen, Rep. Brit. Assoc, 1841, p. 190. 



1842. Raphiosaurus, R. Owen, Trans. Geol. Soc. [2], vol. vi, p. 413, pi. xxxix, fig. 3. 



1850. Raphiosaurus lucius, R. Owen, in Dixon, Geol. Sussex, p. 385, pi. xxxix, figs. 1 — -3. 



1851. Raphiosaurus subulidens, R. Owen, Rept. Cret. Form. (Mon. Palaeont. Soc.), p. 19, pi. x, figs. 

 5, 6. 



1889. Pachyrhizodus subulidens, A. S. Woodward, Ann. Mag. Nat. Hist. [6], vol. iv, p. 351. 

 1901. Pachi/rhizodus subulidens, A. S. "Woodward, Catal. Foss. Fishes B. M., pt. iv, p. 43, pi. vii, 

 figs. 1, 2. 



Type. — Anterior portion of maxilla ; Sedgwick (Woodwardian) Museum, Cam- 

 bridge. 



Specific Characters. — A small species, the maxilla attaining a length of about 

 10 cm., the mandible about 15 cm. All teeth slender, very smooth, with the apex 

 inwardly and backwardly curved. Maxilla flattened externally, with sockets for 

 from 30 to 40 teeth ; premaxilla expanded into a triangular facial lamina. Dentary 

 bone very deep, but rapidly contracting in front into a narrow thickened sym- 

 physis ; its outer face remarkably smooth, marked with two deep longitudinal 

 depressions between which the middle part of the bone projects in a rounded 

 longitudinal ridge ; its total number of tooth-sockets not less than 30. 



Description of Specimens. — The type specimen (PI. XXVII, fig. 2), which is the 

 anterior part of a left maxilla, was originally described by Owen as the dentary 

 bone of a lizard. A similar maxilla of the right side has been found in association 

 with part of a dentary (B. M. no. 385G6), thus identifying the latter element; 

 while another maxilla is associated with a clavicle and scales. These specimens 

 prove that the head represented in PI. XXVII, fig. 1 , belongs to the same species. 



In the latter fossil the cranium lacks the ethmoidal region and is incomplete 

 behind on the right side, but it exhibits its principal characters when viewed from 

 above (fig. 1 a). The external bones are nearly smooth, marked only in part by 

 the radiating structural lines, which are most conspicuous in the depressed middle 

 area of the frontal region. The supraoccipital (socc.) is exposed in a short and 

 broad band at the back of the cranial roof, and bears a large median vertical crest 

 on its hinder face. The epiotic {epo.) is also partially seen from above, forming a 

 prominent angle. The parietal (pa.) is a small nearly square bone at the postero- 

 external border of the frontal, Avidely separated from its fellow of the opposite side. 

 The squamosal (sq.) is larger, but its precise shape and extent are not shown. 

 Judging by appearances in the fracture on the right side, the parietal and 

 squamosal join the hinder part of the frontal in forming the roof of ati extensive 

 posterior temporal fossa. The frontal bones ( fr.) are especially large, and their 

 shape and contour are well shown in fig. 1ft. They are constricted above the 



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