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



The first thoracic somite is described and figured by Dr. "Woodward 

 as parallel-sided in lateral view, but a slight depression of the head 

 might probably produce the wedge-like outline seen in the specimens 

 figured above, the first somite being overlapped by the side-plates of 

 the second somite. 



The difference in the form of the legs is much more likely to be 

 significant. In one of the co-types of the species, that represented 

 in Fig. 3 on p. 886 of Dr. "Woodward's paper, and now in the 

 British Museum collection, the endopodite of the penultimate leg is 

 well displayed, and the large segment on the proximal side of the 

 ' knee ' (probably the merus) is less than four times as long as broad. 

 In a specimen in Mr. Egginton's collection, represented in Fig. 3 

 above, the corresponding segment of the penultimate leg appears as 

 if it were at least ten times as long as broad. A careful examination 

 of both specimens, however, does not convince me that they are 

 exactly comparable in this respect. The apparent broadening of the 

 limb in the one case may be somewhat exaggerated by compression, 

 while, on the other hand, a flattened segment might not display its 

 full width if it happened not to lie exactly in the plane of fracture 

 of the matrix. I think, therefore, that the evidence is inadequate to 

 justify the separation of the Coseley specimens as a distinct species 

 from that described by Dr. Woodward. 



Comparison with Palceocaris. — The genus Palceocaris was established 

 by Meek & Worthen in 1865 * for a single species, P. tt/pus, of 

 which a figure was published by the same authors in 1868. 2 The 

 species was discussed at greater length and a restoration given by 

 Packard in 1886. 3 Other species have since been referred to the 

 genus, but they are too imperfectly known to require further con- 

 sideration here. 4 



The restoration of Palceocaris typus given by Packard and reproduced 

 here (Fig. 4) agrees very closely with the original figures oiPrceanas fides 

 as regards the segmentation of the body. It differs chiefly in the form 

 of the thoracic legs, of which six pairs are shown, having the endo- 

 podites very slender and the exopodites broad, flattened, and each 

 divided into three segments. For the reasons given above I cannot 

 regard the apparent slenderness of the endopodites as important, and 

 it may be significant that in Meek & Worthen' s original figure the legs 

 are represented as much stouter than in Packard's restoration. In this 

 character and in the form of the exopodites the Coseley specimens 

 described above agree remarkably well with Packard's figures, the 

 only important divergence being that the segments of the exopodites 

 are more numerous. This, however, is a point on which it is very 

 easy to be misled, and it is not unlikely that Packard may have 

 overlooked some of the delicate lines of articulation. The greater 



1 Proc. Acad. Nat. Sci. Philadelphia, 1865, p. 48. 



2 Geol. Surv. Illinois, iii, p. 552. 



s Mem. Nat. Acad. Sci. Washington, iii (2) ; Mem. 15, pp. 129-33, pi. iii. 



4 It is possible that Palceocaris Burnettii, H. Woodward (Geol. Mag., 

 Dec. II, Vol. VIII, 1881, p. 533, PI. XIV, Figs. 3a, b), might prove to be identical 

 with tbe species discussed here, but the specimen from which it was described 

 is probably too imperfect to make sure of this. 



