210 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Jan. 7, 



Locality. — Schists at the base of the " Orthoceratite and Grapto- 

 lite flags," Pinwhapple Glen, Ayrshire, = Tipper Bala. 



There can be no doubt, from the style of armature and ornament, 

 and from the general appearance of this form, even without the 

 assistance of the head, that it belongs to the genus Acidaspis. The 

 structure of the tail is that of A. Keyserlmgi ; only the ridge, which 

 usually traverses the pygidium, and joins or forms the primary spine, 

 is still farther expanded at the expense of all the flat portion of the 

 appendages of the first joint of the tail-axis. 



Only ten body-rings have hitherto been noted in any species of 

 Acidaspis, and nine is the more usual number ; the number twelve, 

 therefore, in this species, is a singular characteristic. A. unica forms 

 a very welcome link between Acidaspis and the Cheiruridce, already 

 in many respects closely allied. 



None of the species of Acidaspis described in former works have 

 hitherto occurred in the Silurian rocks of the South of Scotland. 



EXPLANATION OF PLATE VL 

 (The specimens are reversed in the Hthograph.) 



Figs. 1-5. Acidaspis Lalage. 1-4. Twice the natural size. 5. Much enlarged. 

 From specimens in my own collection. 



Figs. 6-10. Acidaspis hystrix. 6. Much enlarged, from a small specimen. 7, 8. 

 Twice the natural size. 9. Much enlarged. 10. Represents the 

 supposed arrangement of the double row of spines. The specimen 

 fig. 8 is from Ihe Survey Collection ; the others are from my own. 



Figs. II, 12. Acidaspis callipareos. II. Partially restored, and twice the natural 

 size. 



Figs. 13, 14. Acidaspis unica. 13. Twice nat. size. 14. Much enlarged. 



Figs. 15-17. Acidaspis Car act aci, 15,16. Natural size. 17. Much enlarged. 



5. On two Silurian Species o/* Acidaspis, /;'o»z Shropshire. 

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



[Plate VI. figs. 15-17.] 



I TAKE the opportunity afforded by my friend Dr. Thomson's paper, 

 to add a figure to his plate, and a notice of two species, which will 

 help to complete the account of the genus. They have been pre- 

 viously quoted in the second edition of Morris's Catalogue ; but one 

 has not been figured, and the other not described. 



1. Acidaspis coronata, sp. nov. 



A. Briffhtii, Salter, Mem. Geol. Surv. vol. ii. pt. 1. p. 348. pi. 9. 

 figs. 8 & 9 only ; A. coronatus, Salter, Morris's Catal. 2nd ed. p. 99. 



A. lata, fere uncialis, capite angulis latis productis, nee a genis abrupte di- 

 stinctis : glabella angusta ; lobis sejunctis, — basalibus medianum aequanti- 

 bus : cer\ace mutico ? : oculis parvis retrorsum tractis : cauda transversa 

 brevissima, spinis 8, — primariis modicis, terminalibus 4, externis utrinque 1 ; 

 omnibus parallelis. 



