[MATTHEW] STUDIES ON CAMBRIAN FAUNAS 183- 



var. ANGiLiMBATA, 11. vav. (PI. III., tigs. 3 a and b.) 



The form we suppose to represent this species is of the size of the 

 type, and nearly the same proportions ; it diflers in having a narrower 

 anterior marginal fold. It has two obscurely marked glabellar furrows, 

 like Billings's species, and shows the same narrow area in front of the 

 glabella; it ditl'ers in that the ocular tillet is scarcely raised above the 

 level of the cheeks, but as Billings's type is a cast (in sandstone), the fillet 

 is more distinct than in ours. There is a distinct tubercle on the middle of 

 the neck ring in the Acadian variety, and the glabella is obtusely carinate 

 along the median line. The posterior glabellar furrows on some examples 

 are scarely discernible. The eyelobes are long, and are about as far from 

 the posterior margin of the head as the width of the occipital ring. 



Sculj^ture. — The surface is minutely granulate, except in the 

 furrows. 



/S<~e.— Length of the head-shield, 6h mm. ; width of the middle 

 piece at the eyes, 7| mm. ; at the back of the shield, 8h mm. 



Horizon. — Dark sandy layers in the black shales. 



Billings's type is not by any means perfect, as his figure does not 

 show the back of the lixed cheeks. This part in the St. John form is 

 narrow, being finside of the eyelobe,) only half as wide as the glabella, 

 and the posterior angles are not much extended. The neck i-ing is wider 

 than shown by Billings's figure for the Vermont example. 



Walcott makes Billings's C. arenosus a variety of C Adamsi, but the 

 latter's figures and descriptions preclude us from accepting such a con» 

 elusion. 



SoLENOPLEURA EoBBti, Hartt, mut. PARVA. (PI. III., tigs. 4(/ and 6.) 



Conocephalites Robbii Hartt, Acad. Geol., •2nd Ed , p. 648. 

 Ptychoijaria Robbii, Wale, U. S. Geol. Surv., Bull. 10, p. 36, pi. vi., tig. 1. 

 Solenojileura Robbii, Trans. Roy. See, vol. v., pt. iv., p. 1.5.3, pi. ii., figs, 'èa to I 

 and 4a to e. 



There are a few heads which appear to agree in the pro])ortion of 

 the parts and the contour, with Hartt's species above cited. They are 

 however, considerably smaller than those of that species. They resemble, 

 also, Angelin's S. hrachymetopa, but are not more than half of the length 

 of that species. 



Horizon. — Found both in the limestone bands of the gray shale and 

 in the overlying black shales. 



