THE FAUNA OF THP: ST. JOHN GEOUr. 1S9 



The head-shield iu all its parts is narrower. The dorsal furrow is deep and nearly 

 connects with the anterior marginal furrow. The glabella is about a fifth longer than 

 wide, and the three furrows turn backward. The posterior marginal furrow is more 

 open. 



A pygidium, with a stronger rachis than that described with the broad form of this 

 species, and having five joints in the rachis and a narrow margin, is supposed to belong to 

 this form. 



In the broad and narrow forms of this species we have variations that are parallel to 

 those of S. Robbii and 8. Orestes of the lower horizon ; but the two species (S. Robbii and 

 S. Acadica) are not the same, as they are distinct by their surface markings as well as by 

 difference of form. The sculpture also distinguishes this species from S. covtmiinis, Bill. 

 In its leather-like .surface (best seen on the cheeks) this species may be compared with 

 S. bruchymetopa, var. ahUiceu, Brogg. ; but the Acadian species differs in its smaller glabella, 

 more slender rachis, and longer and strongly geniculated pleura3. From S. crisfafa, Linrs., 

 it is distinguished by its broader fixed cheek, its smaller glabella, its deep dorsal furrow, 

 and by having an ocular fillet ; and from both of these species, by having points or 

 spinelets at the genal angles. 



Horizon unci LoccilUy. — Same as for the broad form. 



The figures on Plate II of this article give a better presentation of this species than 

 that on Plate VII of the former article, that having been a composite figure, combining the 

 features of the broad and narrow form, but chiefly the former. 



Var. ELONGATA, n. var. (Plate II, fig. 6.) 



A fine example of this form shews the body to be oval, with short spines at the genal 

 angles. 



The head-shield is longer iu proportion and the dorsal suture more sinuous. The 

 middle piece is more prolonged both in front and at the posterior angles. The most 

 marked difference however is in the unusually long glabella, somewhat enlarged toward 

 the base and carrying four furrows ; the glabella is about a half longer than wide. 



The thorax has fourteen or fifteen joints, and the rachis is unusually narrow and 

 long ; the pleurae run flat for more than half their length and are then suddenly genicu- 

 lated ; each pleura is usually considerably more than twice the length of the axial ring, 

 and the extremity is rounded. 



The pygidium is broadly lenticular, having a prominent but not wide rachis, ex- 

 tending to the end of the shield ; there are six joints iu the rachis, and of these the first is 

 almost detached, there being a suture marking it oft" from the rest of the pygidium, the 

 second and third rings are prominent, but the thi-ee last are smaller and less distinctly 

 divided than those which precede them. The side lobes have four grooves, the first on the 

 anchylosed segment, pleura-like, the second distinct and broad, the third fainter and the 

 fourth short ; the three last furrows do not reach the margin of the pygidium. 



If the anchylosed segment on this pygidium be counted with the thorax, it will 

 increase the number of segments in that part by one (fifteen in all), and leave the number 

 in the pygidium normal for the narrow form of a Solenopleura. 



