MACROPOMA MANTELLII. 33 



near their bases a shallow groove, in which series, at first single, 

 of rounded pits appear. In each of these pits a short pointed spine 

 is fixed. 



More towards the distal end of the fin-ray the rows of pits and 

 spines become double, those of the two sides usually alternating. 

 In no specimen I have met with does a fin-ray present any indu- 

 bitable articulation. It is probable that the extreme ends were 

 articulated, but the length of unjointed fin-ray is remarkable in 

 Macropoma, as compared with Holophagus and Ccelacanthus. 



The first dorsal fin is supported by the single lamellar inter- 

 spinous bone (Plate VII., fig. 1), which is as characteristic of the 

 Coelacanths, as the forked interspinous bone of the second dorsal 

 (Plate VII., fig. 1), indicated by Agassiz. The true form of 

 the first dorsal bone is best exhibited in No. 4,260 of the British 

 Museum, which shows it to be plough-share shaped, the anterior 

 margin being oblique, and much longer than the posterior. 

 Several ridges radiate from its upper edge downwards and for- 

 wards to its anterior inferior angle and inferior edge. 



The Pectoral and Ventral Fins. — The pectoral fins are supported 

 by a very strong bone, curved so as to be concave forwards, flattened 

 from side to side, and giving off a process upwards and backwards, 

 po as to appear bifurcated above. (PI. VII., fig. 4 b.) 



The ventral end of each pectoral arch widens out in a direction 

 transverse to the axis of the body, and becomes concave from side 

 to side behind, so that this part of the bone takes on much the 

 appearance of a marrow spoon. This is particularly well seen in 

 No. 4,251 of the British Museum Collection. 



I have met with only one specimen of the chalk Macropoma 

 which shows the structure of the pectoral fin distinctly. In this 

 (Coll. British Museum, 4,258) the right pectoral is thrown 

 forward, and seen from the inner side (Plate VIL, fig. 5). The 

 rays, about 20 in number, decrease in strength from before 

 backwards, and their inner ends are so arranged as to show that 

 they fringed an obtuse lobe. On this no trace of scales was 

 discernible, but the left pectoral, which is imperfectly preserved, 

 shows the remains of a covering of small scales with a tubercu- 

 lated ornamentation. 



The pelvic bones are very long, and each has, at its base, a strong 

 process directed at right angles to the axis of the bone, and 

 meeting its fellow of the opposite side (Plate VII., fig. 1). 



There is a specimen showing a ventral fin in the British 

 Museum (No. 25,944), in which the fin-rays are so disposed as to 

 lead me to believe that it was lobate. 



The fin-rays of the paired fins do not seem to have possessed 

 the spinous ornamentation along their anterior edges, which is seen 

 in the median fins. 



The Skull—The roof of the skull (Plates VIL, fig. 1, VIII., 

 fig. 2), is divisible in Macropoma, as in Ccelacanthus, into two 

 moieties, an anterior or frontal (B), and a posterior or occipito- 

 16295. 



