118 F. R. Coirper Reed — Evolution of Cheirurus. 



is almost rectangular or slightly wider in front, and the side- 

 furrows are distinct. From the first side-furrow of the glabella 

 a prominent ridge runs to the eye. The eye is for the most 

 part large, situated in the middle of the cheek, with rounded 

 triangular eye-lohe without an oblique furrow at the base. The 

 genal angles are produced into long horns. 



Group 2 consists of the somewhat heterogeneous subgenus 

 Cyrtometopus. All the species have a longitudinal furrow on the 

 inner part of the pleurae. The marginal furrows of the head- 

 shield do not run into the axal furrows, or only pass feebly 

 over the anterior wing of the fixed cheek. This swollen anterior 

 wing of the fixed cheek on the inner side of the anterior branch 

 of the facial suture is an important feature. The shape of the 

 glabella varies considerably : thus, in Cyrto. Plautini (Schmidt) 

 it is parallel-sided, reminding one of Cheirurus (sens, str.), while in 

 Cijrto. clavifrons (Dalni.) and Cyrto. offinis (Ang.) it is oval. The 

 side-furrows of the glabella are always distinct, and the basal lobe 

 is incompletely circumscribed, except in Cyrto. pseudohemicranium 

 (Nieszk.) which has a broad and deep third side-furrow completely 

 surrounding the basal lobe. This species also has an almost obsolete 

 first side-furrow to the glabella. 



The strange subgenus Sphcerocoryplie (which probably ought to 

 take generic rank) is closel}' linked on to the true Cyrtometopus by 

 Cyrto. pseudohemicranium and Cyrto. aries (Eichw.) ; but the extra- 

 ordinary inflation of the anterior position of the glabella, the teeth 

 on the lateral margin of the head-shield, and the reduction in the 

 number of the thoracic segments (8-11? but commonly 9), suffi- 

 ciently distinguish it. 



Section II of the whole genus Cheirurus, according to Schmidt, 

 includes three subgenera — NieszkowsJcia, Pseudosphccrexochus, and 

 Eccoptocheile. The subgenus Nieszkoivslcia is made by Schmidt to 

 receive certain species which had been placed by Nieszkowski in the 

 genus Splicer exochus, and by Angelin in Cyrtometopus. N. cepha- 

 loceros (Nieszk. sp.) may be taken as the type. 



The characters common to the whole section are the possession of 

 twelve thoracic segments; the absence of any constriction of the 

 pleurae, so that they lie close to one another along their whole 

 length; the presence of a longitudinal row of puncta, 1 instead of 

 a furrow on the inner portion of each pleura ; the presence of a 

 narrow articulating band on the anterior border of the inner portion 

 of each pleura ; and the abrupt termination of this band without 

 a hamate process. There is a feeble indication of this band on the 

 posterior border of the head-shield. The three subgenera form 

 three groups. 



Group 1 consists of the subgenus NieszTcoiosTiia. In this subgenus 

 the glabella is swollen posteriorly, and often passes into a hump or 

 spine. All the side-furrows are directed backwards, and the third 

 side- furrow, which is stronger than the other two, runs in a curve 

 towards the neck-furrow, but does not reach it. The free cheeks 

 1 In Pseudospluerexochus these puncta are very faint or absent. 





