232 R. T. POCOCK. 



is laterally constricted, then expands into a subcircidiU' softei' 

 plate, to the ragged edge of which are fastened many 

 muscles passing to the pregenital somite and to the 

 appendages of the sixth pair. Sometimes at least there is, on 

 the upper side of this plate, a pair of short processes which 

 serially repeat apparently the longer tendons of the anterior 

 part of the entosteruite. From tlie underside in front arise 

 two pairs of processes, the first passing from the anterior ex- 

 tremity of the cornua to the coxae of the cheUe, the second 

 to the presternum from a point on a level with the anterior 

 bridge (PI. 13, figs. 2, 9). 



The figure and description of the entosternite of Thely- 

 plionus published by Laurie (8) do not agree with this 

 organ in the species examined by myself. The anterior three 

 pairs of dorsal processes and the two pairs of ventral pro- 

 cesses, as well as the lateral crest, are omitted from the figure 

 and unmentioned in the text ; and I find no process pro- 

 jecting from the sides of the posterior lobe such as he 

 represents and describes. iSo, too, is the figure twice 

 published by Schimkewitsch (9, 10) from a sketch by 

 Tarnani and copied by Bernard (3) unlike, in certain particn- 

 lars, the entosternites of the Tlielyphonida; I have dissected, 

 althougfh resembliuo; tliem in general form and in the 

 number of the processes. For example, the bifid process 

 numbered 8a.' in my drawing is represented as rising from 

 the side of the anterior bridge slightly behind the level 

 whence the processes numbered 2tg. diverge; and the pro- 

 cesses numbered 3/^. spring further back in line with the 

 posterior bridge, not jnst behind the middle of the larger 

 foramen, as shown in my di'awing. The lateral crest, too, 

 was apparently unnoticed. Considering the uniformity 

 in the structure of the prosoma throughout the family Thely- 

 phonida), it seems hardly probable that these discrepancies 

 are due to specific differences between the specimens examined. 

 I find a practically complete uniformity of structure in tlie 

 entosternite in species of the genera Thelyphonus, 

 Hypoctonus, and Mastigoproctus. 



