A. Smith Woodward — Fish Fauna of Purbeck Beds. 149 



length to the base of the caudal fin. The maximum depth of the 

 trunk is twice that of the caudal pedicle. 



Head mid Opercular Apparatus. — Though much fractured, the head 

 has precisely the aspect of that of Macrosemhis, and the straight 

 parasphenoid, parallel with the hinder part of the cranial roof, is 

 distinctly shown in section. A few large styliform teeth occur in the 

 short jaws ; while below and behind the ceratohyal some slender 

 branchiostegal rays are preserved. 



Axial Skeleton of Trunk. — The persistence of the notochord is 

 indicated by the vacant space between the neural and haemal arches of 

 the axial skeleton of the trunk ; but there are robust small hypocentra 

 and pleurocentra, especially conspicuous in the abdominal region. 

 Ribs are shown extending not quite to the ventral border of the 

 abdomen ; and the hsemal arches in the caudal region are very stout 

 at the base of the caudal fin. It is difficult to count the vertebrae, 

 but there cannot have been less than thirty -five. 



Appendictdar Skeleton. — Portions of all the fins are shown, but the 

 caudal and pectorals are especially fragmentary. The pectoral fin-rays 

 are very long compared with those of the pelvic fin, which is small 

 and situated much nearer to the anal than to the pectorals ; the much- 

 expanded proximal end of the pelvic support is observable. Unless 

 the state of preservation is deceptive, the dorsal fin arises slightly 

 further back than usual in the genus, above the fifth pair of ribs ; but 

 there seem to be stout fin-supports in advance of this, and some rays 

 may thus, perhaps, have been accidentally destroyed. The number of 

 rays distinguishable is about twenty-five, and they are all slender, 

 showing distant articulations, though no clear evidence of bifurcations, 

 while the length of those in the caudal region apparently does not 

 exceed the depth of that part of the trunk ; the supports are com- 

 paratively robust, tapering and curved forwards at their lower 

 extremity. The anal fin, as ordinarily, is quite small, comprising 

 only seven or eight rays. 



Squamation. — There are remains of very thin scales over the whole 

 of the trunk, but nothing can be ascertained of their characters. Of 

 the large fulcral scales at the base of the caudal fin, only one 

 imperfect example can be seen above and below. 



Specific Determination. — The fish thus described most closely 

 resembles a small species from the Upper Portlandian of Savoimieres- 

 en-Perthois, Meuse, France, described by Dr. Sauvage under the name 

 of Macrosemius pectoralis} The counterpart of the type specimen of 

 this form has recently been acquired by the British Museum, and so 

 admits of direct comparison. The Purlieckian fish, however, is only 

 about two-thirds as large as that from the French Portlandian, and is 

 distinguished by its more robust caudal region, perhaps also by the 

 smaller number of rays in its dorsal fin. The fact that its hinder 

 dorsal fin-rays are not observed to bifurcate, as they certainly do in 

 the French fish, may be due to imperfect preservation. The smaller 

 degree of ossification of the vertebral elements may or may not be due 

 to the immaturity of the new specimen. In any case, the proportions 



1 H. E. Sauvage, Bull. Soc. Geol. France [3] vol. si. (1883), p. 477, pi. sii. 

 fig. 17. 



