Professor C. E. Beecher — Earypteriis in the Cambrian. 563 



These differences are considered as indicative of a new genus, and 

 it is proposed to recognize this type under the name Strabops, nov. 

 gen., with Strabops Thacheri, n.sp,, as the type species. The generic 

 name is in allusion to the inward turning or squinting of the eyes 

 (ffTyoaySo's ' squinting ' and oyjm ' face '). 



Doubtless many generic differences will appear when the 

 appendages of this type are obtained. The differences in the 

 characters available for comparison are quite as great as between 

 JEurypterus and Dolichopteriis, Stylonurus, Anthraconectes, or 

 Eusarcus. This, taken with the fact that practically all the 

 Cambrian genera, especially the more highly organized types, 

 became extinct long before the Upper Silurian, lend support to 

 the conclusion that Strabops is generically distinct from any hitherto 

 known form. 



Strabops Thacheki, gen. et sp. nov. 



Body broadly ovate in general outline exclusive of the telson, 

 slightly convex in the specimen, though probably quite arched both 

 transversely and longitudinally in life, as indicated by the outline 

 of the separate segments. 



Cephalothorax short and broad, length less than one-half the 

 width, anterior and lateral margins regularly rounded, posterior 

 margin gently curved in the middle and turning obliquely forward 

 toward the genal extremities, which are obtusely angular. 



Eyes medium-sized, ovate, narrow ends pointing obliquely inward, 

 situated in the middle of the anterior half of the cephalothorax, 

 distant about the length of one eye, connected anteriorly by a distinct 

 arched line or fold. The eye tubercles are mostly exfoliated, and 

 their convexity and surface cannot be determined. Ocelli indicated 

 by two spots midway between the eyes. 



Abdomen. The dorsal side shows eleven segments exclusive 

 of the telson. The axis in the specimen is slightly convex, and 

 slopes off into the nearly flat pleural region without any line of 

 demarkation. The greatest width is across the third segment. The 

 extremities of the segments are rounded anteriorly and on the sides, 

 and terminate behind as a simple angulation. The first six segments 

 are quite uniform in length, while the three following are somewhat 

 shorter, and the last two are a little longer. 



Telson a broad flat spine, obtusely elevated along the middle. 



Surface smooth, with an indication of a row of minute crenulations 

 or scale-like markings near the posterior edge of each segment. 



Dimensions. — Greatest length of specimen 110 mm., length ex- 

 clusive of telson 82 mm. ; greatest width, allowing for compression 

 on left side, 60 mm.; length of cephalothorax 20 mm., width 

 49 mm. ; greatest width of telson 17 mm. 



Formation and locality. — From the lower members of the Potosi 

 limestone. Flat Kiver, St. Francois County, Missouri. 



The only known genus of merostomes besides Strabops occurring 

 in the Cambrian is Aglaspis, Hall, represented by two species 

 {A. Barrandi and E. Eatoni, Whitf.). But since Aglaspis belongs 



