THE LOWER CHALK OE DOVER. 445 



they radiate from its extreme posterior angle; and, further, the 

 inner lateral process of the fishes' skull is usually believed to contain 

 part of the superior vertical semicircular canal, and the normal place 

 for the epiotic is upon the summit of this canal. The bone occupy- 

 ing the usual position of the pterotic is large, and extends a long way 

 up towards the middle line of the skull, the radiating lines passing 

 upwards and forwards from the hinder and outer portion. The 

 extent of this bone is shown best in fig. 1 (pt.ot) ; the edges on the 

 left side are broken, and, as here represented, may possibly include 

 part of the parietal. "When perfect, as on the right side, the pterotic 

 appears to join the frontal and to cover much of the epiotic ; the 

 sutures, however, cannot be traced. The postorbital process occupies 

 the position of the sphenotic ; and its lower and proximal part gives 

 attachment to the hyomandibular. Within the orbit, and well under 

 the skull, there is a bone which seems to join the sphenotic, and may 

 be the alisphenoid. The other parts of this region are not visible. 



Vertebrae. — The bodies of five vertebrae have been exposed, although 

 only four of them are visible in a side view (fig. 1). In general 

 form and structure they agree with those of PortJieus, the bases of 

 the neural arches being lodged in deep depressions ; and the heads of 

 the ribs, or perhaps ossicles intervening between the ribs and the 

 vertebrae *, appear likewise to be inserted in similar depressions ; 

 and there are lateral depressions between the ribs and the neural 

 arches. The vertebra marked 7 is the most perfect, and is probably 

 the seventh from the skull. This vertebra has a long deep depression 

 on the side, situated a little below the base of the neural arch, and 

 a much smaller one just below the hinder end of the larger one. 

 The centrum is proportionally longer than in Portheus gaultinus 

 (vol. xxxiii. pi. 22. f. 10), being about 0-65 inch long and 0'5 inch 

 high. The vertebra marked 6 has lost the small lateral depression ; 

 and the rib-ossicle, which is covered with pyrites, extends further 

 up the side of the centrum. 



Daptinus, species ? 



There is a right maxillary bone, also in the British Museum 

 (no. 42017), from the Lower Chalk of Dover, which agrees so closely 

 in form with the maxilla of the specimen above described, that there 

 can be little doubt of its belonging to the same genus. The specific 

 identity of the two specimens, however, is very questionable ; for 

 this maxilla has the outer surface ornamented with fine granulations 

 and pittings. The hinder portion, where probably it was overlapped 

 by a jugal, wants these markings, and presents instead a few large 

 oblique undulations or ridges. 



* Prof. Cope states (/. c. p. 207) that, in Ichthyodectes anaides, these depres- 

 sions accommodate short ossicles, to which the ribs are attached ; and it is poa 

 sible that the same arrangement may obtain in the present instance also. 



