[bell] new genus of CHARACEAE AND NEW MEROSTOMATA 163 



Original curvature of carapace destroyed by pressure but a 

 raised gastric region still indicated. The lateral margins are bordered 

 by a depressed band which broadens towards the antero-lateral 

 corners. Anteriorly a distinct V-shaped cervical furrow joins the 

 two flat marginal bands and divides the carapace into two unequally 

 sized areas. The anterior of these areas has three distinct spine-bear- 

 ing ridges, a median one forming the base of the rostrum, which runs 

 for half the distance to the cervical fold, and a pair of lateral ridges 

 on either side, which are directed so as to converge when produced at 

 a point near the forward end of the rostrum. These ridges abut on 

 the cervical furrow but do not quite reach the anterior margin. The 

 area behind the cervical furrow is marked by a very faint median keel 

 which dies out entirely half a millimetre from the posterior border. 



The surface viewed through a lens is roughly pitted, and the 

 bases of larger spines lie on the rostrum and keels. 



Dimensions: Extreme length 20 mm. ; length, excluding rostrum, 

 along median line, 13 mm.; length of rostrum projecting beyond anterior 

 margin 5 mm.; width of rostrum at anterior margin 0.8 mm.; greatest 

 width of carapace 17 mm. ; apex of cervical furrow 7 mm. from the 

 anterior border. 



Locality: St. Rose mine, Inverness county, N.S. From roof of 

 coal seam, associated with Naiadites, Ostracoda, and Palaeochara 

 acadica. 



Horizon: Coal Measures. (Lower Coal Measures?) 



Remarks: Although the type specimen of A . hillianus is propor- 

 tionally narrower than the present one, the points of agreement are 

 too many for varietal separation. Peach^ has pointed out that in 

 A . russellianus the serrations on the lateral margins are most probably 

 the flattened spines that were borne along the whole length of lateral 

 keels. As a result of the doublure of the test, and flattening accom- 

 panying fossilization, the serrations may appear to be restricted to 

 the anterior portion of the carapace. This observation promotes 

 caution in laying stress on the number of dentations visible on the 

 margin, stated to be five on the type specimen of A . hillianus. The 

 two strong spines figured by Dawson on either side of the base of the 

 rostrum are seen in the present specimen to consist of two short 

 spinous keels as present also in a similar position in A. russellianus 

 and other species. 



Dawson pointed out the close resemblance of A. hillianus to A. 

 duhius (Prestwich) . Yet the afifinity must lie nearer A . grossarti Salter 



^Peach, B. N., Monograph on the Higher Crustacea, Mem. Geol. Surv. G.B. 

 Pal. Vol. I, No. 1, pp. 31-32, pi. iv. Figures 4, 6, 1908. 



