32 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Nov. 20, 



It is therefore with, great pleasure that I lay before this Meeting 

 an entirely new form, which I have referred to the genus Encrinurus, 

 from the Cock's-comb Mountains at the Cape, collected and forwarded, 

 together with some new and singularly interesting reptilian remains 

 and other fossils, to the British Museum by Dr. W. Guybon Ather- 

 stone, F.G.S, of Graham's Town, Cape of Good Hope. 



The specimen is preserved in a nodule of about the size of a 7 lb. 

 cannon-ball, and exhibits on one piece tbe dorsal aspect of the seg- 

 ments of nearly the entire body, save that the head is folded under, 

 on the other a profile of the fossil in intaglio, which gives a most 

 instructive view of the Trilobite, and shows that originally each of 

 the eleven thoracic segments was probably furnished with a median 

 dorsal spine five lines in length, giving to it a crested appearance 

 suggestive of the specific name of crista-galli — a name doubly ap- 

 propriate, as the specimen was obtained from the Cock's-comb 

 Mountains. 



The caudal series, or pygidium, although not furnished like the 

 thoracic series with a row of dorsal spines, is terminated by a 

 caudal spine rather more than | an inch in length. These spines 

 are rendered still more novel from the fact that they are annulated 

 from their bases to their tips, thus giving them much the same 

 aspect as the little Silurian Annelide tubes known as Tentaculites 

 annulatus. 



The axis of each thoracic ring is moreover ornamented by the 

 addition of from two to three tubercles on either side of the great 

 central spine, and with from four to five tubercles on the ridge of 

 each of the pleurae. 



The axial ridges are very prominent, as is also the raised pos- 

 terior portion of each of the pleurae ; the anterior fulcral portion 

 of each rib is also clearly seen divided by a deep furrow, as are each 

 of the thoracic segments from the preceding and succeeding somite. 

 The margins of the pleurae are slightly expanded ; and their lateral 

 borders appear to have been obtuse. 



Each of the eight segments composing the pygidium has its axial 

 and pleural ridges ornamented in like manner with tubercles ; the 

 furrows between the axial ridges are also proportionally deep. We 

 cannot describe the head, save to observe that the surface was 

 covered with rounded tubercles — a character seen in other Encrinuri. 



The occurrence of spines is by no means a rare feature in the 

 ornamentation of Trilobites ; the genera Homalonotus, Arges, Acid- 

 asjpis, Lichas, Bronteus, are familiar examples ; but Sao hirsutus, of 

 Barrande, a Lower Silurian (Bohemian) form, alone has such a line 

 of axial spines as is seen in this form from Africa. 



But the spines in Sao are very minute, and extend moreover con- 

 tinuously along the axis of the pygidium also, which is not the case 

 with the African species. The number of the segments, as well as 

 their form and that of the pygidium, point to Encrinurus (and not to 

 Sao) as the genus for the reception of this crested species. . Nor is it 

 altogether anomalous ; for in our British Encrinurus punciatus 

 specimens occur with one, two, and even three axial spines on the 



