1857.] THOMSON — ACIDASPIS. 209 



From our specimen, it appears that the neck-segment is evidently 

 prolonged, but it is unfortunately broken off before reaching its 

 spinous armature. Head richly granular. 



Locality. — Mullock Hill sandstone, Girvan, Ayrshire. I believe 

 this sandstone to be an equivalent of a portion of the Upper Bala 

 group still higher than the ** Graptolite and Orthoceratite flags." 

 In mineral, and to a certain extent in palseontological, character it 

 seems to pass into the Saugh Hill sandstone, which is rich in the 

 typical Caradoc forms, Encrinurus punctatus, Briin. sp., Cyphaspis 

 megalopSy M'Coy, sp., Pentamerus oblongus, Sow., Atrypa hemi- 

 sph(Brica, Sow., Tentaculites annulatuSy Schloth., Beyrichice, &c. 



This species is evidently closely allied to A. pectinata of Angelin ; 

 indeed we must put great faith in the correctness of the figure in the 

 * Palaeontologia Scandinavica,' to draw a distinction between them. 

 The general form of the glabella is the same in each. In A. calli- 

 pareos the posterior lateral glabellar lobe is much larger than the 

 anterior ; in A. pectinata the lobes are represented as nearly equal. 

 This is unusual, and might prove a fallacy arising from some imper- 

 fection in the specimen figured. 



Both species are closely allied to A. Dama, Fletcher and Salter, 

 MS.* ; but in A. Dama the eyes are much more remote than in 

 A. callipareos, and the head is altogether broader and shorter, more 

 allied in general form to A. Brightii and the A. bispinosa group. 



The outline of the head of the present species is more like that of 

 A. Dormitzeri, Barr., than of any described British form. The eyes 

 in A. callipai^eos were pedicellate. 



A. callipareos closely resembles Ceraurus (A.) crenatus, Emme- 

 rich, especially Loven's figure in the Stockholm ' Ofversigt.' It is 

 distinguished from it by the narrowness of the anterior triangular 

 space within the ocular ridge. 



AciDASPis UNICA, sp. nov. PI. VI. figs. 13, 14. 



A. segmentis duodecim, tuberculosis, unispinosis, antice latis, postice 

 angustioribus ; cauda minuta, bisegmentata. Capite — ? 



Head wanting. The entire form, including the tail-spines, must 

 have been | inch long. Body-rings twelve ; lateral portions hori- 

 zontal ; a double ridge runs along the lateral portion of each seg- 

 ment, the two ridges coalescing at the distal extremity, and ending 

 in a strong, long, reflexed spine ; the spines nearly uniform in length. 

 Axis of body-rings very convex. Axis and lateral portions orna- 

 mented with a double row of minute granules. 



Tail short, consisting of two minute segments. Lateral append- 

 ages of first segment slightly expanded, twisted backwards at a right 

 angle about ^th of their length from the axis. A shallow groove 

 passes through the centre of the shghtly granulated expanded portion. 

 The appendages of the second tail-segment are lost ; they probably 

 supported a fringe of short equal spines. 



* Morris, Catal. Brit. Foss. 2nd edit. p. 99. 



