barton: a new genus of the cheiruridae. 551 



backward. Each pleuron is divided by a node-like constriction into 

 an inner third and an outer two thirds. The inner third is subrectan- 

 gular and cut by a diagonal furrow. The outer two thirds is long, 

 tapering, and somewhat lanceolate. 



Measurements. — Length of cephalon 27 mm. 



Width of cephalon at neck-ring 55 =*= 



Length of glabella 20 



Width of glabella at frontal lobe 16.5 



Width of glabella at basal lobe 17.0 



Position of the eyes 



Ratio of dist, eye 1 to the posterior margin 



to the length of the cephalon .... . 44 

 Ratio of dist. eye to glabella to the length of 

 the cephalon . 26 



This species is apparently allied to Ch. icarus Billings, but is dis- 

 tinguished from that species by the unisolated basal lobes of the gla- 

 bella, by the broader margin of the cephalon, and by the more slender 

 and tapering pleura. 



Formation and Locality. — The Richmond of the Province of 

 Ontario. The type (M. C. Z. No. 12 Walcott collection) is probably 

 from Manitoulin Island, Lake Huron. 



Ceraurinus icarus (Billings). 

 Plate, fig. 7. 



Cheirurus icarus Billings, Can. nat. & geol., 1860, 5, p. 67, fig. 2. 



Ceraurus icarus Meek, Ohio pal., 1873, 1, p. 162, pi. 14, fig. 2a, b, c. 



Ceraurus meekanus Miller, N. Amer. geol. & pal., 1889, p. 537. 



The name Ceraurus meekanus was proposed by Miller for the forms 

 figured by Meek from Richmond, Indiana, as C. icarus Billings. This 

 form must, however, be referred to Ch. icarus Billings. 



Miller, in his definition of C. meekanus, says, "distinguished [from 

 Ch. icarus Billings] by the form of the glabella, by the furrows, struc- 

 ture of the thorax, and form of the central lobe, and by the pygidium, 

 besides occurring in higher rocks and growing to a much larger size." 



Billings's figure of Ch. icarus is poor, and his type is lost, but his 

 description is most minute. The pertinent points of it are: — glabella 



1 From tip of palpebral lobe. 



