56 Messrs. Hancock & Howse on Janassa bituminosa 



in the mouth. One of the specimens was quite perfect wlien 

 found ; but unfortunately an idle lad got hold ot it, after the 

 quarryman had carefully laid it aside, and in the mere lack of 

 thought broke away a great number of the teeth. Happily, 

 however, the anterior portions of nearly the whole of them arc 

 still left sticking in the matrix ; so that not only their num- 

 ber can be ascertained, but likewise the exact limit of those be- " 

 longing to the upper and lower jaws respectively, and their 

 precise arrangement thereon. 



This specimen tif the buccal armature was not only complete 

 when deposited, Init is lying on the slab in its natural posi- 

 tion ; and probably when buried the whole fish was present, 

 and lay with its back uppermost. Consequently, the mouth 

 being situated beneath, as in the Sharks and Rays, the teeth 

 of the overhanging upper jaw would lie in advance of those of 

 the lower. Such is the case in the specimen now before us, 

 as is determined by the presence of a quantity of shagreen, 

 indicating as it does the direction in which the body of the 

 lish was deposited. There are about three inches of this sha- 

 green, extending from the posterior margin of the mass of 

 teeth, or those which belong to the under jaw. And, in fact, 

 there can be little doubt that, had the slab been continued 

 backwards sufficiently far, we should have had an impression of 

 the whole lish, marked out by the shagreen, similar to the 

 figm'c given by 3Iunster of his Dictca striata. 



The cutting or anterior margins of the teeth are downwards, 

 for the most part buried in the matrix. Many of the roots 

 and, to a great extent, the crushing-disks having been removed, 

 as before stated, the specimen is, as it were, hollowed out, and 

 presents an oval, disk-like aspect, an inch and three-quarters 

 long, and an inch and a quarter wide. The broken anterior 

 portions of the teeth line this cavity in almost perfect order, 

 as if observed from the interior of the mouth, their external or 

 anterior extremities being tm-ned from the observer. The 

 group thus seen is divided into two portions, an anterior and 

 posterior. The teeth of the former or upper jaw have their 

 faces or anterior scoop-like cutting-margins and crushing- 

 disks, or as much of them as is left, turned downwards, and 

 are closely packed together in five horizontal rows of seven 

 teeth each. The central teeth of the five rows rest one upon 

 the other in the median antero-posterior line, diminishing in 

 size forwards and upwards as the specimen is seen. These 

 five central teeth are flanked on either side by three others, 

 which likewise diminish in size in front. These teeth, of 

 which there are in all thirty-five, as already stated, belong to 

 the upper jaw. A similar cluster of teeth belongs to the under 



