/. — Pleuracanthidce. 715 



indicates the largest example of the genus known ; and compared with the complete 

 examples obtained from the strata of Bohemia or Commentry, the Newsham fish 

 must have been between three and four metres in length. 



. The lower jaws are 0--15 m. in length, the posterior part of the jaw is O'll m. 

 in height, and diminishes to about half that amount anteriorly. As in the lower 

 jaw exhibited in Plate lxv., its posterior portion appears to have had centres of 

 ossification bounded by more or less angular borders (fig. la), and giving it the 

 appearance of being composed of a series of plates. The left jaw (fig. 1^) is in a 

 normal position, the right has been to some extent flattened out, which gives a more 

 largely expanded surface than it probably possessed in a natural state. The outer 

 borders of the two lower jaws correspond in position with those of the upper 

 jaws exhibited on the opposite side of the slab, and the latter have impressed 

 their form on the former, giving them the appearance of having a thicker border 

 than they really possess, but for which they would no doubt have got credit 

 had the specimen been less perfect. Numerous teeth are scattered between and 

 about the jaws. The right ramus of the lower jaw is somewhat broken, as shown 

 in the figure, but the depression of the surface (fig. la a) may indicate the position 

 where articulation has been. A thickening of the bone appears to show that the 

 articulating surface was in its immediate vicinity. 



To the right of the left mandible (fig. \b) there are two or more large cranial 

 plates. The one marked (fig. \d) is 0*20 m. in length and 0"13 m. in breadth; it 

 has a convex outer margin corresponding in curvature with the inner one which 

 is concave. Both ends of the plate were probably attached to other bones ; the 

 outer convex margin is thicker and stronger than the other parts. The form of 

 this plate is similar to the one marked (a) in Mr. Dinning's specimen (PL lxvii., fig. 2) 

 which occupied a position on the margin of the cranium in a line with the occipital 

 plates. Another large osseous plate (fig. le) occupies an area in advance of the one 

 described. The mass is 0'24 in length, and may consist either of a single plate or 

 more probably of two ; it is more rectangular than the one mentioned before, and 

 probably extended in front of it towards the anterior part of the skull. 



The opposite side of the specimen is no less interesting. The palato-pterygoid 

 constituting the upper jaws are exposed as well as the cranial plates marked 

 d and e of the figures of the other side. The outer margin of the jaws is nearly 

 circular (PI. Lxvi.), and from right to left the diameter is 0'43 m. A line drawn fi'om 

 the symphysis of the rami to the posterior extremities of the jaws is 0*44 m. in 

 length. The outer margin of the jaws is thicker than the remaining portion, and 

 as previously observed has impressed its form on the opposing lower jaws. The 

 posterior extremity of the right jaw, which is perfectly exposed, is narrow, the 

 inner margin being concave and the diameter 0*07 m. at a distance of 0'07m. 

 from the end. From that point it rapidly expands and joins up to the opposing 



