171 

 DESCRIPTION OF THE PTERIGOTUS PROBLEMATICUS, AGASS. 

 By J. W. Salter, Esq., F.G.S. 

 The limbs of this interesting fossil not having been hitherto discovered, 

 the specimen found by M, Scobie at the Hagley Park ^Z^T^t 

 interest as connecting it satisfactorily with the species ^^^ 

 Agassiz which was obtained from the basement beds of the Old Bed Sandstone 

 XTfarshir, But though of the same genus with the Scotch fossil, it pre- 

 sents characters which separate it specifically. 



As there are on the same slab with it numerous epecunen. of Awula re 

 trofiexa Orthis lunata, and OrUcula rugata, there can be , no doubt of its 

 big •; the Upper Ludlow rock; and we are therefore ^srified m consider^ 

 it's belonging to the species which is so common (though always in a frag- 

 mentary^! ^ the same stratum throughout Shropshire, HereforAhire, and 

 The MaTvern Hills; a fragment of the carapace of which is figured by Agassiz 



(Sa *E£ii££l on the slab the best preserved is that of a finger 

 probably the fixed one. It is two and a half inches long, and seven and a half 

 lies broad, exclusive of the spines, and of equal breadth throughout ; but it 

 nllr shew, the base nor the tip, and must have been considerably longer. 

 The IsLce is very thin, sections of the broken ends showing this condition 



"^ Opines along the inner edge are long, conical, or almost cylindrical 

 and are set fully their own breadth apart ; they are of various si.es, several 

 small ones being interposed between the larger spine, There are seventeen 

 of the smaller spines on the fragment, each about a line high ; there are two 

 larger ones about a quarter of an inch in length, and one larger spine toward 

 the middle, which is broken, but its bone is a quarter of an inch broad AU 

 the spines turn a little backward, as in Pterygoid Anglicus, and are finely 

 striated lengthwise, rather obliquely. The surface of the finger itself » very 

 ill-preserved and crushed. It appears not to have been quite smooth, and 

 there are scattered small tnbercles towards the inner edge, as well as minute 

 prickles interspersed between the spines. 



In P. Anglicus, as figured by Agassis, the spines are much larger and 

 more coarsely striate, and they stand so close together that their phases often 

 touch; they are, too, fewer in number than in our fossil, and the finger is 

 shorter than this appears to have been. 



The other fragment is more doubtful ; it has spines along the margm 

 like the last, but they are much larger and more closely placed, so that then: 

 bases approach each other. There are also small prickles interspersed ^as n 

 the last; but the margin on which they are set, instead of being slightly 

 concave, is considerably convex, and unless it has been ^ much curved by 

 pressure, could hardly have belonged to the extremity of the limb. On this 

 fragment, but probably not connected with it, there is a large conical spine 

 or articulation constricted at its base. It is an inch long by five lines broad, 



