Dr. W. T. Caiman — Syncarida from Coal-measures. 491 



Traces of other mouth-parts are seen in some of the specimens, 

 and in one (Fig. 2, A) they resemble so closely the mouth-parts of 

 Anaspides (Fig. 2, B) as seen from the side that there can be little 

 hesitation in identifying the metastoma (lower lip), maxillida, and 

 maxilla. 



The eight pairs of thoracic limbs all appear to be slender in the 

 specimens examined. Those of the first pair are only obscurely seen 

 and appear to be very short ; the others successively increase in length. 

 The apparent slenderness of these limbs in comparison with those of 

 the type-specimens of P. precursor will be discussed later. 



Several specimens show traces of exopodites on the thoracic limbs, 

 and they are very clearly seen in the specimen figured (Fig. 3). 

 They are flattened and lanceolate in outline, about 1*5 mm. in length, 

 and - 2 mm. across the widest part. Each is divided into a number of 

 short segments, which are broader than long except towards the tip. 

 JNo traces of marginal setae are preserved. No exopodite can be seen 

 on the last thoracic leg, and it is probable that this limb was devoid 

 of an exopodite as it is in the living Anaspidacea. 



FlG. 3. Palceocaris precursor. Portion of thoracic region showing legs and 

 exopodites. From specimen No. 19 in Mr. Egginton's collection. X 6. 

 en. endopodite ; ex. exopodite ; II, second thoracic somite ; vill, eighth 

 thoracic somite. 



The remains of the pleopods are somewhat obscure. The uropods 

 are not well displayed in any of the fossils, but, as far as can be seen, 

 they agree with the original description of P. precursor. 



Comparison with Prceanaspides precursor. — The specimens described 

 above agree closely with the original account of P. precursor in the 

 form and segmentation of the body, and in the general structure of 

 the appendages as far as these are available for comparison. They 

 differ in their generally smaller size, the absence or obscurity of the 

 transverse striation of the somites, the wedge-like outline of the first 

 thoracic somite as seen from the side, and the greater slenderness of 

 the thoracic limbs. As regards the first of these points, none of the 

 specimens now examined can have much exceeded 16 mm. in length, 

 while one of the co-types of the species reached a length of 57 mm. 

 Dr. Woodward, however, mentions • specimens of 15 mm. and even 

 10 mm. in length. The absence of striation on the somites may not 

 improbably be due to a difference in the condition of preservation. 



