On Some New Palæozoic Crinoids from England and Scotland

Abstract

The two following species appear to me to be new, and come likewise from the carboniferous limestone:—1. Hydreionocrinus Woodianus. De Koninch. Pl. IV. fig. 5, 5a.The head of this species is of medium size, sub-cylindrical in form, and terminated at its upper part by a crown composed of fifteen pieces, disposed in a circle, and attached one to another, the central space being occupied by the dome. The calix, taken by itself, resembles a little open cup. The base is composed of rather small plates, most of which have a point attached to the stem. The subradial plates, with the exception of that on the anal side, are much broader than long. They are very thick and strongly arched, and consequently their sutures are very decidedly exhibited. The first radial plates are pentagonal in shape, about a third broader than long, and, like the preceding, rather thick, and separated from each other by a strong groove. The second radial plates are also pentagonal, and broader than long. The axillary plate is very thick, and furnished with a slight protuberance, and juts outwards. The brachial plates, which follow the axillary plate, offer nothing remarkable. The external surface of these plates is indented with little irregular tracings, which make it rough, and the test thus resembles shagreen. The arms—twenty in number—are composed of cuneiform alternating articulations, and are joined together laterally. I have not observed any traces of pinnules. The little plates of which the dome is composed are all ornamented with a prominent tubercle in the middle. Their surface is apparently smooth, their number variable, and their form is generally hexagonal. I have not been able to discover any traces of a horn or proboscis, nor of any anal or buccal opening. It is probable these were situated between the arms, which were placed on the anal or irregular side of the bulb, and that these arms were capable of extension, and of admitting a passage for the food of the animal. The stem is rather stout, in comparison to that of most of the other species, among which it is often very slight.