530 Br. Arthur Smith Woodward — ■ 



and there are a few scattered examples. Like the hsemals, they are 

 loosely inserted in pits which extend nearly the whole length of the 

 centra. As shown also by Hay,' each arch consists of a pair of thin 

 laminae, right and left, loosely apposed in the median plane, and 

 surmounted by a long and slender neural spine, behind which 

 a smaller and shorter rod-like process also rises upwards. Each arch 

 slightly overlaps or clasps that next following, but without so well- 

 defined a facet as that represented by Hay. Above some of the 

 neural arches there are remains of the curved free fin-supports. 

 In the caudal region both the neural and hsemal arches are firmly 

 fixed in the pits of the vertebral centra as* far as the origin of 

 the caudal fin. Though longitudinally extended at their base of 

 insertion, they do not overlap or interlock, but the tail is strengthened 

 by the sharp backward curvature and inclination of all the neural and 

 haemal spines. The base of each neural arch is a little triangular 

 expansion, strengthened by a vertical lateral ridge, but not bearing 

 any posterior process, and not in contact with the next arch of the 

 series. The base of each haemal arch is shaped almost like the 

 parapophysis in the abdominal region, but the haemal spine is directly 

 continuous with it.'^ The haemal arches within the caudal fin are 

 much thickened, in close contact, and articulate with the corresponding 

 centra in open sutures. 



There are no intermuscular bones in the caudal region or below the 

 vertebral column in the abdominal region ; but some may perhaps occur 

 among the confused remains in the dorsal part of the abdominal region. 



The left clavicle is seen from within, and exhibits the characteristic 

 long and slender precoracoid arch crushed upon its inner face. Below 

 it the base of the left pectoral fin appears, showing the bases of the 

 four stout anterior rays in their natural position. The same rays of 

 the right pectoral fin are well displayed lying over the ribs, the 

 longest equalling in length a chain of about eighteen vertebrae. All 

 these rays are gently arched bony rods, flattened on the outer 

 face and marked only with a few longitudinal striations, evidently 

 due to their structural fibres. The first, second, and fourth rays 

 appear to be nearly complete to their distal end, where they 

 scarcely taper and lack all traces of transverse articulations. The 

 first ray is the stoutest and largest, with a sharply though 

 irregularly rounded anterior border ; the second ray is at least half 

 as wide as the first ray, and its slender distal end, split by crushing, 

 is preserved in the fossil to a greater length than the latter; the 

 third ray, though seen on the left, is restored on the right si<]e, 

 but it is clear that its distal end cannot have been much expanded ; 

 the fourth ray is less stout, and shorter than the others. Behind 

 these rays in another specimen in the British Museum (jSTo. P. 

 10611) the pectoral fin is completed by three or four very short rays, 

 which expand distally into a finely divided and articulated portion. 



The pelvic fins are preserved apparently in their natural position, 

 arising beneath about the forty-eighth vertebra. They are less than 



1 0. P. Hay, Zool. Bull., vol. ii, p. 51, figs. 15, 16, 1898. 

 * See figures by O. P. Hay, Zool. Bull., vol. ii, p. 48, figs. 13, 14, 1898 

 (in which the hsemal arch is described as neural, and vice versa). 



