488 Dr. W. T. Caiman — Syncarida from Coal-measures. 



II. — On some Crustacea of the Division Syncarida from the 

 English Coal-measures. 



By W. T. Calman, D.Sc. 



I. Paljeocaris precursor (H. Woodward). 



Among the Crustacea from the Coal-measures of Coseley, near 

 Dudley, which have been lent to me for examination by Mr. Walter 

 Egginton, are a number of specimens of a form probably identical 

 with that described by Dr. Henry Woodward l as Praanaspides 

 precursor. These specimens make it possible to supplement, in some 

 important particulars, the original account of the species, and throw 

 fresh light on its relations to the living Syncarida. Reasons are given 

 below for regarding the genus Prceanaspides as a synonym of Palceocaris, 

 Meek & Worthen. 



Description of the Material. — The fossils are contained in nodules of 

 clay-ironstone, and in most cases the parts of the animal are represented 

 by cavities in the matrix, exposing the inner surface of the exoskeleton 

 when the nodule is split open. The cavities are usually lined with 

 a brownish film, probably representing the substance of the exoskeleton, 



FlG. 1. Palceocaris precursor (H. Woodw.). Specimen No. Sin Mr. Egginton's 

 collection. X 4^. a', antennule ; a", antenna ; e. eye-stalk ; ex. part of 

 exopodite or scale of antenna ; I, first thoracic somite ; VIII, eighth thoracic 

 somite ; 1, first abdominal somite ; 6, sixth abdominal somite. 



and are more or less filled in places by deposits of pyrites and of 

 a soft white substance, probably ferrous carbonate. The cavity of the 

 abdomen in some specimens contains an elongated cylindrical body 

 which may perhaps represent the fossilized contents of a capacious 

 intestine. 2 



1 Geoe. Mag., Dec. V, Vol. V, p. 385, 1908. 



2 It may be useful to give some notes on the methods that have proved most 

 effective in the study of these fossils. A Zeiss binocular dissecting microscope 

 was used, and the cleaning of the specimens with needles was aided by 

 cautious applications of hydrochloric acid. The interpretation of the hollow 

 parts is greatly facilitated by taking impressions in modelling wax, but it has to 

 be borne in mind that these impressions of the inner surface of the exoskeleton 

 do not give accurately the relief of the outer surface, for example, in the relation 

 of the mandible to the side-plate of the head, as shown in Fig. 2, A. In some 

 cases the parts of the fossil (e.g. the thoracic exopodites) are distinguished from 

 the matrix by a difference of colour, not of relief. These are seen most clearly 

 if the surface be wetted and a thin cover-glass placed on it. 



