NEW SPECIMEN OP PHOLIDOPHORtfS. 151 



England has hitherto yielded most materials for this study from 

 its Lower Jurassic Formations, particularly from the Lower Lias of 

 Lyme Regis ; while the adjoining Continent, on the other hand, 

 has furnished comparatively few specimens of so early a date, but 

 a very fine series from the Upper Jurassic, notably from the 

 Lithographic Stone (Lower Kimmeridgian) of Bavaria. At last, 

 there seems some prospect that discoveries in the English Upper 

 Jurassic will soon rival even the latter ; for many examples of 

 Pholidoplwrus are now known from the Purbeck Beds of Dorset- 

 shire, and others are gradually being recognised in the Oxford and 

 Kimmeridge Clays. One fragmentary specimen obtained by Mr. 

 Nelson M. Richardson from the Oxford Clay at Chickerell, near 

 Weymouth, is an interesting addition to the increasing series, and 

 forms the subject of the present communication. 



The fossil in question (see accompanying Plate, fig. 1) is a 

 vertically crushed and flattened specimen of the head and abdominal 

 region entirely divested of enveloping matrix. The head is very 

 imperfect and wants the end of the snout. The fractured remains 

 of the cranial roof-bones, the mandible, opercular bones, and bran- 

 chiostegal rays, exhibit an extremely fine tubercular, partly rugose 

 ornament. The right mandibular ramus is comparatively well pre- 

 served (fig. 1), showing the very short articulo-angular element (a#.) 

 uniting in a jagged suture with the long dentary (d.), which is 

 marked by a series of pores indicating the course of the slime canal 

 at the bottom of a shallow longitudinal groove. The dentary is 

 much fractured, and the transverse section near the anterior end 

 shows the characteristic inward reflection of the oral margin ; the 

 single series of closely-arranged, small, conical teeth, with back- 

 wardly curved apex, is also distinct (fig. la.) The opercular and 

 branchiostegal apparatus is too imperfect for description, and 

 no gular plate can be distinguished ; but the uppermost five 

 branchiostegal rays (br.) are shown to be much larger than the 

 others, and even the foremost are laminar and imbricating. 



Behind the opercular plates (op., s.op.) there are crushed remains 

 of enlarged post-clavicular scales, ornamented like the other external 



