Stenhouse. — On the Anatomy of the Pig-fish. 117 



triangles uniting in a thick bar, which meets its fellow in a 

 strong symphysis. The posterior part of the bar bears a long 

 process, extending both in front and behind, and meeting its 

 fellow in a long second symphysis. 



8. Vertebral Culumn. — The vertebral column consists of 

 thirty -six undoubted vertebras and a hypural, supporting 

 tvv'enty-nine or thirty dorsal interspinous bones, 8-10 ven- 

 tral interspinous bones, and twenty -eight caudal rays. 

 The short amphicoelous centrum is a well - ossified cylin- 

 der, with lateral strengthening ridges. The perforated 

 neural processes bear small anterior zygapophyses. Behind 

 each main haemal process there is a small free subsidiary 

 process. Above the level of the nerve foramen the atlas 

 bears a riblike bone, the position of whose head seems to 

 correspond to that of the epineural of Owen. Similar bones 

 for the following vertebrae are attached to processes succes- 

 sively more distinct, and springing from lower levels, until on 

 No. 5 they spring from the centrum. In No. 6 there appears 

 a small bone attached by fibrous tissue to the middle of the 

 undersurface of the riblike bone, usurping the position of the 

 end of the latter over the coelome. The ventral element 

 is longer in No. 7, and nearer the centrum, which it reaches in 

 No. 8, where it has the position of an ordinary true rib. In 

 9-12 the dorsal riblike bone is smaller, and is now clearly 

 "intermuscular." Thus it would appear that the first five 

 vertebrae have no true ribs, but only intermuscular bones. 

 Now, compare the last dorsal and first caudal vertebras 

 (Nos. 15 and 16). The former has its transverse processes 

 very low down, and connected below (as also occurs in 13 and 

 14) by a bony bridge separating the caudal artery from the 

 vein. No. 16 has a complete haemal arch, partially marked 

 into two divisions for the artery and the vein. No. 15 has a 

 pair of ribs, lying close together, parallel to the large haemal 

 spine of No. 16. This spine is grooved in front, and lateral 

 markings seem to point to a homology to the ribs of 15. The 

 hypural consists of a demicentrum with neural and hjemal 

 canals, and two fanlike plateS; of which the upper bears two 

 partially ankylosed pieces like neural spines. The pterygio- 

 phores or interspinous bones of the dorsal have each a 

 triangular body with two lateral supports, and a head con- 

 sisting of a horizontal plate. This plate bears an articular 

 surface, behind which arises a curved process entering the 

 perfect ring of the head of the dorsal spine, and almost 

 meeting a long process from the head of the preceding 

 plate. This amounts to the interlocking of two rings. The 

 four anterior pterygiophores form a sutured structure lying 

 above the skull, but, by boiling, the parts are separable from 

 each other and from the spines. The first, however, having 



