Page:TransRoySocCanada 16 4 159-167.djvu/7

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Dimensions: Greatest length 15.3 mm.; greatest width across genal angles 21.2 mm.; width across median ocellar mound 18.7 mm.; distance of median node from the posterior margin 6.4 mm.; distance of compound eyes from the posterior margin 7.5 mm.; long axis of compound eyes 3.1 mm.; short axis of compound eyes 1.5 mm.

Locality: Roof of four-foot seam, from dump derived from old slope, New Campbellton, Cape Breton.

Horizon: Upper Coal Measures or Radstockian (Upper Westphalian).

Remarks: Eurypterids are rare fossils from the Coal Measures the world over, and only some dozen species have been recorded.

The present species and an allied English Radstockian species Glyptoscorpius kidstoni Peach have carapaces agreeing in size, relative proportions, and ornamentation to that of Anthraconectes mansfieldi C. E. Hall from the Alleghany series. The resemblance is particularly close to those variants of smaller size figured by Jas. Hall as A. stylus. Specific identity, however, is withheld since nothing is known about the body of the Nova Scotian form. Accordingly, emphasis is placed on slight differences in outline of the carapace, distinctions that probably are inconstant and of doubtful specific value. The shield of our specimen has been so flattened by pressure that the anterior margin is covered, and accordingly it was not determined whether a short anterior spine similar to that borne by A. mansfieldi was present. The ornamentation of A. brasdorensis is identical in plan to that of A. kidstoni. In fact, the latter carapace differs only in its slightly greater proportional length and in the presence of a shallow indentation on the posterior border.

A carapace of an Eurypterid has not hitherto been described from the Coal Measures of Nova Scotia. Salter,[1] however, in 1863, assigned some fragments of Merostomatan abdomens to this genus, viz., E. ? pulicaris from the Little River group of St. John, N.B., a fragment of a large body segment comparable to E. scouleri Hibbert, from Port Hood, and an incomplete telson from Joggins whose resemblance to that of Hastimima whitei White from the Coal Measures of Brazil has been pointed out by Clarke and Ruedemann. The excellent preservation of the present carapace leads to the hope that the same horizon may yield further, and more complete, specimens of these ancient arachnids, whose race was rapidly approaching extinction.

The tendency of the Carboniferous Eurypterids to form dermal scale-like excrescences is given phylogerontic significance by Clarke and Ruedemann. Also these authors regard the subgenus Anthraconectes to be fresh or brackish-water inhabitants. A. brasdorensis

  1. Salter, Quart. Jour. Geol. Soc., Lond., vol. 19, pp. 78-79, 1863.