BRITISH FOSSILS. 



PLATE II. ; ALSO PLATE XIII. FIGS. 1-4 ; PLATE XV. 

 FIG. 1. 



SECTION 2. PTERYGOTUS. 



PTERYGOTTJS ACUMINATUS. 



P. magnus, 3-pedalis, elongatissimus, capite oblongo angulis quadratis, 

 oculis rotundis minoribus: segmentis corporis 12, quorum quinque anticis 

 transversis bicarinatis, reliquis subquadratis, penultimo oblongo; cauda 

 ovata in apiculum longum producta. 



SYNONYMS. P. acuminatus, SALTER, Quart. Geol. Journal, 1855, 

 vol. xii. p. 29. fig. 4. P. maximus, id. p. 28. fig. 3. Slimonia (1856), 

 D. PAGE, Advanced Text-Book, p. 135. fig. 3. 



That the two figures above referred to belong to one and the 

 same species is, I think, almost certain, and all the fragments in our 

 Plate II., &c., occur in juxtaposition, and are doubtless remains of 

 the same large Pterygotus, the finest of the four or five species 

 which were collected from Lesmahago by Mr. R. Slimon. Although 

 not so gigantic as those next to be described, P. acuminatus is 

 yet a very large species, and more elongated in all its parts than 

 any of the others. The head is nearly five inches broad and six and 

 a half long, and the seven hinder or abdominal rings, which are 

 different in shape from the anterior thoracic ones, are almost square 

 instead of transverse ; while the tail is ovate anteriorly, and behind 

 is drawn out into an apiculus equalling the anterior portion in 

 length. 



The Head, Plate II. fig. 1., is oblong, with straight sides, except at 

 about the anterior third, where it is contracted so as to give it a 

 suburceolate shape ; the front is somewhat rounded, and as well as 

 the sides crenated, or rather tuberculated along the edge ; the eyes 

 are placed at the anterior angles, as forward as in P. anglicus, but 

 much smaller in proportion, oval, about six-tenths of an inch long, 

 and very prominent. 



Of the body rings, which are twelve in number, including the 

 tail joint (telson), we have several good specimens. Of these the chief 



