Dr. W. T. Caiman — Syncarida from Coal-measures. 489 



In the most complete specimen (Fig. 1) the body, of which the side 

 view is exposed, is about 16 mm. in length, and is curved so that the 

 dorsal edge is convex in the thorax and concave in the abdomen. 

 Eight thoracic somites are visible behind the head, followed by six 

 abdominal somites and the telson. 



The head (Fig. 2, A) is about 1-8 mm. in length and the same in 

 depth at the hinder edge. It is produced in front into a very short 

 rostrum, beneath which the margin shows a distinct concavity no 

 doubt representing the orbital notch. The lower margin appears to 

 overlap the bases of the mouth-parts as a pleural fold, although this 

 cannot be clearly seen on the internal aspect as exposed in the fossils. 

 On the side of the head a very distinct groove (represented by a ridge 

 on the inner surface) runs vertically upwards from the basal angle 

 •of the mandible, but dies out before reaching the dorsal surface. 

 A horizontal groove, starting from the hind margin at about the 

 middle of its height, runs forwards for a short distance, but does 

 not reach the vertical groove. In the specimen represented in Fig. L 



m & mx^' mt 



mx: 



mx 



,mt. 



PlG. 2. Lateral aspect of head-region. A. Palceocaris precursor. Drawn 

 from a wax impression of specimen No. 15 in Mr. Egginton's collection ; 

 the side-plate of the head would overlap the base of the mandible if the 

 actual outer surface were seen. X 5. B. Anaspides tasmania. x 6. 

 a!, antennule ; a', antenna; e. eye; h.gr. horizontal groove; md. 

 mandible ; rfi.gr. mandibular groove ; int. metastoma ; mx'. maxillula ; 

 mx". maxilla ; r. rostrum ; I, first thoracic somite ; II, second thoracic 

 somite. 



this horizontal groove is obscured by a strong fold that runs for 

 the whole length of the head, but this is evidently due to crumpling 

 of the exoskeleton. The vertical and horizontal grooves seen in 

 Fig. 2, A, however, are certainly normal features and are seen in several 

 of the specimens ; their significance will be discussed below. 



The first thoracic somite is very short, its dorsal margin being only 

 about half as long as that of the succeeding somite. In side view it 

 is wedge-shaped, narrowing below so that the fore edge of the second 

 somite almost touches the head at its lower end. It is possible that 

 the line defining the first somite from the head may indicate a suture 

 rather than a movable articulation, for no overlapping of the edges 

 can be observed. 



The remaining thoracic somites differ in length among themselves, 

 but owing to the varying degrees of flexion or extension of the body 

 in the different specimens it is not easy to determine the exact 



