The single specimen at hand somewhat resembles I. maximns Locke from 

 the Ordovician of the United States of America. As the latter is now considered 

 to represent only a stage in the development of Isotclus gigas Dekay without 

 genal spine,^' it is only provisional that I establish a new species on the 

 present specimen. 



Locality : — No-lu-ping, Tung-hu-lisien, prov. Hu-pei (Usui Coll.). 



Illaenidse. 



Illaenus, Dalman. 



Illaenus sinensis Yace sp. nov. 



PI. xvni., Fig. lo. 



191 1. Illnoius sp. Fkech : in Ricirnioi'KN'.s China, vol. V., p. 3. " 



Cephalon semielliptical, nearly twice as broad as long ; smooth all 

 around convex, with the anterior portion strongly bent down almost 

 to the right angle, and the lateral sides more gently sloping to the margin. 

 Posterior margin of the cephalon slightly concave in outline. Glabella with 

 independent convexity, and well vaulted at the basal portion ; occupies 

 nearly the middle third of the cephalon and extends less than half its length. 

 Axial furrows well marked, subparallel, first slightly converging toward the 

 anterior end where they curve outward. Plxed cheek with the base nearly 

 as wide as the glabella, palpebral lobe but slightly elevated, rather large in 

 size and relatively close to the posterior margin of the cephalon. I^yes rather 

 large in size. Posterior branch of the facial suture very oblique ; anterior 

 branch ? Free cheeks considerably broader than the fixed cheek and genal 

 angle well rounded ; posterior and intreior borders of the cephalon meeting at 

 the genal angle in an angle of about 65°. Inferior border of the cephalon Hes 

 almost in a plane. Surface bears numerous fine terrace-lines. 



1) Grabau and Shimer: North American Index Fossils, Invertebrates. Vol. II. 1910. p. 94. 



2) G. HjLM: Illaeniden. In Fr. Schmidt's Revision def ostbaltischen Silurischen Triobiten. 

 Mem. I'Akad. Imp. Sci. St.-Petersbourg, VII. Ser., Tome XXXIII. 1886. p. 87, pi. II., figs. 



