22 bulletin: museum of comparative zoology. 



BuMASTUS graftonensis Meek and Worthen. 



Illaenus (Bumastus) graftonensis Meek and Worthen, Proc. Acad. nat. sci. 



PhU., 1870, p. 54; Geol. surv. Illinois, 1875, 6, p. 508, pi. 25, f. 4. 

 Buniastus sp. ind. Meek and Worthen, Geol. surv. Illinois, 1875, 6, pi. 24. f. 3. 

 Illaenus graftonensis Weller, Bull. Chicago acad. sci., 1907, no. 4, pt. 2, p. 223, 



pi. 16, f. 4-6. 



Only the cephalon of this species has previously been known, but 

 the Day collection contains two complete, though somewhat flattened 

 specimens from Waukesha, Wisconsin, where this species seems to be 

 fairly common. 



The cephalon is too well known to need further description, except 

 to note that as in B. ioxus, there is a prominent median tubercle be- 

 tween the eyes and near the posterior margin. 



The thorax has ten segments, a broad axial lobe, rather well-defined 

 dorsal furrows. The pleura of the thoracic segments are more promi- 

 nent and ridged, and not so flat as in most species of Bumastus. The 

 pygidium is short and moderately convex, with a flattening around 

 the margin, but not a real concave border. The pygidium resembles 

 that of B. ioxus, but is shorter and wider, the average ratio of length 

 to width in B. ioxus being .64 and in the two pygidia of B. graftonensis 

 which we have, .54. 



Formation and locality: — Nine specimens (M. C. Z. coll.) are from 

 the Niagaran at Waukesha, Wise, a locality from which this species 

 has not previously been reported. 



Bumastus indeterminatus (Walcott). 

 Plate 2. 



Illaenus indeterminatus Walcott, 31st Ann. rept. N. Y. state mus. nat. hist., 

 1877, p. 19 adv. sheets; 31st Ann. rept. N. Y. state mus. nat. hist., 1879, 

 p. 70. 



Illaenus cf. /. indeterminatus Clarke, Pal. Minn., 1897, 3, pt. 2, p. 716, f. 24. 



Bumastus indeterminatus Raymond and Narraway, Ann. Carnegie mus., 1908, 

 4, p 253, pi. 62, f. 8, 9. 



The M. C. Z. contains the type of this species, and it is figured 

 (Plate 2) for the first time. The specimen consists of a good cephalon, 

 part of one free cheek, a very much dislocated thorax, of which only 

 se\en segments can be definitely made out, and a very fine pygidium. 



