TRIGONOTARBUS. 73 



Anthracosiro fritschi, Pocock, Text-figure 37. 



1903. Anthracosiro fritsvhu, E. I. Pocock, Geol. Mag. [4], vol. x, pp. 405—408, with fig. 



Since no new material of this species has come to hand I can add nothing to 

 the original description. The only known specimen measures 6'5 mm. in length. 



Type in the British Museum (No. I. 1556) from the Coal Measures of Coseley, 

 near Dudley (H. Johnson Coll.). 



Qenus TRIGONOTARBUS, nov. 



Generic Characters. — Body forming an elongated oval, pointed at its anterior, 

 rounded at its posterior end. Carapace high, markedly triangular in outline from 

 above, ^videst at its posterior angles, its posterior border straight, its lateral 

 borders slightly sinuous and converging forwards to the pointed anterior extremity. 

 The median portion of its upper surface forming a flatfish triangular area, from 

 which the lateral and anterior portions slope somewhat abruptly away to the 

 margin ; the lateral portion hollowed posteriorly ; the posterior portion of the 

 carapace depressed and marked with a transverse groove parallel with the posterior 

 border ; the anterior sloping portion compressed, A pair of contiguous eyes on the 

 anterior angle of the flatfish area at the summit of the compressed sloping portion. 

 Opisthosoma slightly convex between the laminge, as Avide as the carapace in front ; 

 its lateral and posterior borders forming an evenly oval curve, consisting above 

 of seven distinct tergal plates nearly equal in length, each marked laterally with a 

 groove defining the lateral upturned laminfe, which are smaller upon the anterior 

 than upon the median and posterior terga, those of the first tergal plate being- 

 very small; the laminse not directed so obliquely backwards as in A?ithracosiru. 

 The last tergal plate with three laminae, the median completely separated from 

 the laterals by the normal angled groove, but not separated by a groove from the 

 main portion of the tergal area. Sternal surface of opisthosoma strongly convex 

 from side to side, forming an even transverse curve across the middle line from 

 the margin of the lamina} of one side to that of the other, but without any lateral 

 groove defining the lamina?. The posterior border of the sternal plates mostly 

 strongly recurved, but the recurvature becoming progressively less and less marked 

 anteriorly ; the sternal plate corresponding to the second tergal plate nearly 

 straight from side to side ; two or three plates in front of this, the number being 

 uncertain, the anterior being triangular and projecting between the coxte of the 

 legs of the last pair ; its posterior border concave, probably marking the anterior 

 rim of the genital orifice. The last plate on the ventral surface bearing the 

 circular anal sclerite. 



10 



