On the Occurrence of the Genus Astrocrinites (Austin) in the Scotch Carboniferous Limestone Series; with the Description of a new Species ( A. Benniei ), and Remarks on the Genus

Abstract

I ntroduction .–In a paper entitled “Proposed Arrangement of the Echinodermata” &c., Messrs. Austin referred to a genus which they proposed to establish under the name of Astracrinites , in the following words:—“Another genus ( Astracrinites of our MS.) offers so many affinities to the recent and fossil Echinodermata, that we consider it the most remarkable of all the known genera. By its being lobed it approaches to the Lobistella ; its ambulacra, spines, and arms mark it as allied to the Echinites , while the arrangement of its calcareous plates connects it with the Lilies of the ocean. In short, it possesses the lobes of a Starfish, the ambulacra and spines of a Sea-urchin, and the plates of a Crinoid. It is further remarkable by deviating from the quinary type so prevalent in the Echinodermata: the lobes and ambulacra of this new genus are each four in number.” In the following year Messrs. Austin described this curious and aberrant form under the name of Astracrinites tetragonus. Their description is as follows :” “Family Astracrinidæ, “Consisting of the genera Astracrinites and Aporocrinites ; “Genus Astrocrinites, Austin. “Def.—Dorso-central plate quadrangular, to which four pairs of elongated plates are attached, imparting a lobed shape to the fossil. In the retiring angles at the base of the four lobes are a like number of ambulacra. Mouth central. Anus lateral. “A. tetragonus, Austin. “Def.—The plates of this species agree with the generic definition. Each of the elongated plates has two or three rows of minute tubercles around its outer margin