430 MR. J. "W. DAVIS ON A NEW SPECIES OP CCELACANTHUS 



connexion "between tbe first and second caudals. The rays of the larger caudal fin are 

 similar to those already described in connexion with the fins of the body ; they are 

 formed of a single pierced ray, connected with the interspiiious bones to be mentioned 

 further on, the distal extremity of which is divided by a number of joints with articulating 

 surfaces. The rays are thirty-eight or more in number, half of which are above and half 

 below the median extension of the vertebral column. The second caudal also consists of 

 a numher of short rays, which form a duplicate in miniature of the larger caudal fin, 

 without the continuation of the vertebral axis beyond its extremity. 



The specimen of which a figure is given on PI. XLVII. fig. 1 affords an almost perfect 

 representation of the structure of the under surface of the head. The anterior external 

 boundary of the specimen is formed by the right and left ramus of the lower jaw (m), each 

 3 - 3 inches in length. The space between the rami of the jaw was wholly occupied, when 

 the fish was living, by a pair of jugular plates (ju) ; these extended from a position imme- 

 diately under the point of contact between the mandibles backwards a distance of nearly 

 3 inches. The external lateral margins of the jugulars fit to and occupy a groove along 

 the under surface of the mandibles, whilst mesially one appears to have slightly 

 overlapped the other : this is indicated by there being no ornamentation on the inner 

 surface of the left jugular, whilst that of the right one extends to the margin of the plate. 

 On either side may be seen the operculum (op), a large subtriaugular bone 1*3 inch in 

 diameter. The under surface is represented in this figure ; the upper or external surface 

 is covered with a beautiful arrangement of stria?, very minute but distinct, feebly repre- 

 sented by a separate operculum on PI. XLVII. fig. 7. In addition to the opercula there 

 are two similar but smaller bones on each side, which were probably connected with the 

 operculum, and may have been suboperculum and interoperculum (s.op and Lop). For- 

 tunately the external hones have been pressed aside and separated, so that the internal 

 arrangement of the branchial arches (br) is exhibited. There are five branchial ossifi- 

 cations, extending diagonally from each side of a median support : they are strong, with 

 a more or less sigmoidal curvature, and vary in length between 1*7 and T2 inch, the 

 anterior arch "being longest, and those placed posteriorly gradually decreasing in length ; 

 they have a diameter of about "2 of an inch. The median support is a strong bone 2 inches 

 in length, "2 of an inch in breadth near the middle, widening out anteriorly to 3 of an inch, 

 and terminating in an acute point : posteriorly the surface expands to - 5 of an inch, and 

 bifurcates at the posterior extremity. A detached specimen is represented by fig. 10 on 

 PL XLVII. Between the two jugular plates aud in front of the median branchial support 

 there is an ossified mass, which may represent the cruciform bone which Prof. Huxley 

 describes as forming the anterior extremity of the strong median ossification in Coelacan- 

 thus Upturns (Memoirs of Geol. Survey, decade xii. p. 19). In this instance, if the mass 

 represents the cruciform extremity, it is a separate bone. The opposite extremity also 

 differs from the enlarged figure in the Decades, which is described as a "posterior elon- 

 gated spatulate portion." 



The specimen drawn on PI. XLVIII. exhibits a further extension of that portion of the 

 body forming the junction of the head with the trunk of the fish. The jaws and jugular 

 plates (ju) are exposed, and extending from beneath these are a pair of bones (x), one on 



