350 MR. A. SMITH WOODWARD ON NEW FISHES [Apr, 15, 



measurement is contained scarcely six times in the total length. The 

 caudal pedicle is also much less robust in this immature Purbeckian 

 fish than in the typical species from the French Lithographic Stone. 



Genus Strobilodus. 

 [A. Wagner, Abh. k.-bay. Akad. Wiss., CI. ii. Bd. vi. 1851, p. 75.] 



Strobilodus purbeckensis, sp. nov. (Plate XXIX. fig. 4.) 



A single example of the head and pectoral arch, with a portion of 

 the abdominal region, exposed from the right lateral aspect, indicates 

 the occurrence of a small species of Strobilodus in the Purbeck beds of 

 Swanage. The specimen is shown of tlie natural size in Plate XXIX. 

 fig. 4, and is unfortunately too much crushed to exhibit many details 

 of its osteology. It adds, however, a few new points to previous 

 observations on the genus. 



Head and Opercular Apparatus. — The head must have been 

 originally somewhat compressed from side to side, longer than deep, 

 and with a pointed snout. The cranium is narrow aud elongated, 

 with a well-developed parasphenoid (pas.) ; aud the cranial roof 

 exhibits no ornamentation, being only sparsely pitted. The pre- 

 ma.villa (pmx.) is evidently short, though much broken, and the 

 maxilla (rmv.) is relatively long and narrow. This element is robust 

 and has a somewhat wavy dentisierous border, its anterior two thirds 

 forming a gentle convexity, this passing backwards into a short 

 concavity, and becoming convex again at the hinder end. The 

 mandible (md.) is also long and narrow, deepest at its articulation, 

 and gradually tapering to its pointed extremity. The mandibular 

 suspensorium is very oblique, but ils elements are obscured by thin 

 ])ostorbital membrane bones, which seem to have attained consider- 

 able proportions and are externally unornamented. The branchial 

 arches and pectoral arch are also covered by the crushed remains of 

 the opercular bones, which likewise exhibit a smooth outer surface. 

 The preopercultim {p.op.) is long, narrow, and gently curved, without 

 a distinct inferior limb. 



Dentition. — A single series of teeth, of large size and well spaced, 

 occupies the whole of the margin of the month above and below. 

 Each tooth is fused with the supporting bone, has a large pulp-cavity, 

 is somewhat tumid at its base, aud ends upwards in a long, slender, 

 tapering apex ; there is also a characteristic median longitudinal 

 depression on the outer aspect of the tumid base of all the principal 

 teeth. The teeth vary somewhat in size, those of the maxilla being 

 largest in the middle of the great convexity, smallest in the concavity, 

 and relatively long, slender, and closely arranged on the hinder 

 convexity. In the mandible, the largest examples are in the middle 

 of the ramus. There are not less than twenty-eight teeth in the 

 upper jaw and twenty in the lower. 



Vertebral Column. — The remains of the vertebrse {v.) are seen in 

 the form of narrow, though robust rings, either complete or nearly 

 so, somewhat angulated, and apparently with slight tuberosities for 



