Geological Survey Professional Paper 58 The Guadalupian Fauna

VERMES.

Genus SPIRORBIS Daudin.

SPIRORBIS TEXANUS n. sp.

Pl. XXVII, fig. 6.

The specimen which forms the subject of this description is somewhat incomplete, but, on the other hand, is very well preserved, so that all the essential characters are readily ascertained. The shell is small, and irregularly and very loosely coiled. It is marked by numerous strongly projecting lamellose collars, which are rather regularly and closely arranged. They are not perpendicular to the surface, but project forward somewhat strongly. There are also very delicate longitudinal liræ, which are not entirely regular and not continuous between the different stages of growth marked by the annular lamellæ.

This species resembles Spirorbis imbricatus Ulrich. It is much smaller and more delicately constructed. The annulations are relatively a little more crowded, while the interspaces instead of being marked by concentric liræ show delicate radiating ones.

Horizon and locality.—Delaware Mountain formation, southern Delaware Mountains, Texas (station 2969).