Page:A Revision of the Families and Genera of the Stylonuracea (Eurypterida).djvu/26

190 The following species are recognized for this genus:

Diagnosis.—Stylonuracea with ventral shield having well developed epistoma; metastoma broadly sub-rectangular, slightly emarginate anteriorly and posteriorly.

Type genus.—Laurieipterus, new genus.

Remarks.—The Laurieipteridae is composed of the genera Laurieipterus, Ctenopterus, Hallipterus and Mazonipterus, all of which are characterized by unusually long carapaces, and were generally grouped together, more or less, under the genus Ctenopterus. Laurie, however, as early as 1899 (pl. 2, fig. 3), had revealed the unusual rectangular metastoma, and this was verified by Waterston (1962, p. 145, text-fig. 3) who also worked out the details of the ventral shield.

The family Laurieipteridae is easily separated from all the other families of the Stylonuracea. In comparison with those families which have a developed epistoma, namely, the Stylonuridae and Pageidae, the greatest dissimilarity lies in the altogether different metastomas. That of the Stylonuridae is very narrow and deeply notched anteriorly, whereas in the Pageidae it is "coffin-shaped," or elongated, with the anterior wider, and both anterior and posterior ends truncated. This is in sharp contrast to the broad sub-rectangular metastoma of the Laurieipteridae.

Diagnosis.—Laurieipteridae of medium-size, carapace enormously elongated, very narrow at the base but with the lateral margins greatly expanded at midsection; anterior rounded with ornamentation of crenulations; lateral eyes small and arcuate, anteriorly located and well apart; ocelli located in front of the lateral eyes; legs powerful and not excessively long; podomere-count: ?–?–7–8–8–8; spines developed on all but last two walking legs, which are completely bare, the spines increasing in length along the posterior side of each joint; ventral shield with well developed epistoma and with triangular transverse