Vol. 52.] SILURIAN SPECIES OF ACIDASPIS. 243 



House, Builth. So far as can be seen, and the specimen is nearly- 

 complete, it is indistinguishable from A. Hugliesi ; but it is difficult 

 to believe that this species can occur so low down in the geological 

 scale. Pencerrig lies close to the boundary between the "Wenlock 

 and Llandeilo Beds, and it is possible that the specimen may have 

 been obtained from the former. 



Acidaspis erinaceus, Marr & Nicholson. 



1888. Acidaspis erinaceus, Marr & Nicholson, Quart. Journ. Geol. Soc. vol. xliv. 

 p. 723, pi. xvi. tigs. 11 & 12. 



This species having been recently figured and described, the only 

 point to which it is necessary to call attention here is that the 

 original of Messrs. Marr and Nicholson's fig. 11 shows, somewhat 

 indistinctly, the frontal border in front of the glabella. The free 

 cheeks are lost in the specimens, and hence the form of the head, 

 with the glabella apparently projecting in front, seems abnormal 

 in the figure. 



The species is compared by Marr and Nicholson with A. centrina, 

 Dalm., from the same horizon in Sweden. 



Horizon and Locality. — Llandovery Beds : in the Acidaspis 

 erinaceus-zoiie of the Stockdale Shales at Torver Beck. 



Acidaspis callipareos, Wyv. Thomson. 



1857. Acidaspis callipareos, Wyv. Thomson, Quart. Journ. GeoL Soc. vol. xiii. 

 p. 208, pi. vi. figs. 11, 12 ; 1878. Nicholson & Etheridge, « Mon. Sil. Foss. Girvan,' 

 p. 125. 



Only the head is described by Wyville Thomson; and it is 

 believed by Nicholson and Etheridge to be probably the head of 

 A. JiystrLv. The two, however, are stated to have been found on 

 different horizons. Wyville Thomson considers A. callipareos to be 

 very closely allied to A. pectinata, Ang. 



Horizon and Locality. — According to Wyville Thomson, the 

 specimens were found in the Mullock Hill Sandstone near Girvan. 

 This is of Llandovery age. 



Two other species, to which Fletcher and Salter l gave the names 

 of Acidaspis Dama and A. dumetosus, are stated to occur in the 

 * Upper Silurian ' at Dudley. No description of them has been 

 published ; and I have been unable to find, in the various collections 

 arranged by Salter, any specimens ascribed to A. dumetosus. In 

 the Jermyn Street Museum several fragments from various horizons 

 are referred to A. Dama, but they are not sufficient to afford a 

 sound basis for the description of the species. The specimens from 

 the Wenlock Shale show a pair of spines springing from the neck- 

 segment, and are clearly distinct from any of the forms here 

 described. 



1 Morris, ' Catalogue of Brit. Fossils/ 2nd ed. (1854) p. 90. 



Q.J.G.S. No. 206. s 



