[MATTHEW] STUDIES ON CAMBRIAN FAUNAS 81 



lobe to a narrow posterior furrow and fold. The furrow runs forward 

 toward the eye-lobe, but a small corner of the fixed cheek separates 

 them, hence the furrow is not quite continuous, it is more so than it 

 appears to be when looked at from above. 



Size. — Length of the head-shield, 8 mm. Width of the middle 

 piece, 10 mm. 



Locality and horizon. — With the preceding. Eare. 



This species, in its narrow upturned margin, recalls M. recurva of 

 the Protolenus Fauna in New Brunswick, but its fixed cheek is pro- 

 portionately wider, its eye-lobe shorter, and its glabella has a much 

 higher relief. 



M. angimargo is much nearer to Solenopleura (?) hombifrons than M. 

 Walcotti is ; nevertheless there are differences in the wider front and 

 narrower posterior measurement of the first ; its flatter cheek, shallower 

 dorsal furrow and narrow occipital ring also separate it. But with 

 M. angimargo in the genus Micmacca, it is more difficult to separate 

 S. (?) bombifrons from it. This last also occurs in the gray calcareous 

 shales (No. 3) at Manuel's, where it is half as long again as the type of 

 the species from the Brigus limestone. 



There is quite a strong general resemblance between this species and 

 the fossil from Parkers Quarry, Vt., which Mr. Walcott has referred to 

 Billings, Bathyurus senectus,^ as Protypus senectus, but it has a much 

 weaker occipital ring and posterior marginal fold than the Parker's 

 Quarry species. It differs much more widely from Whitfield's Angelina 

 Hitchcocki, which is Walcott's type of the genus Protypus. 



AVALONIA, Walcott. 



AVALONIA PLANA, n. Sp. (PI. IV., fig. 7.) 



Only the middle piece of the head-shield is known. This is uniformly 

 convex, both laterally and lengthwise, the arch being about a quarter of 

 a circle and strongest in front. 



The front marginal fold is distinct, and there is no area in front of 

 the glabella, but a sharp furrow extends from its front to the doi-sal 

 suture just under the eye-lobe; the marginal fold is three times as wide 

 here as in front of the glabella. 



The glabella is flattened-cylindrical, slightly widened in front and 

 behind, and has a small projecting [angle, opposite the strong intra- 

 ocular groove ; there are three pairs of furrows, extending one-third 

 across the glabella, of these the anterior is quite faint, but the two 



1 It is not like the examples of Billings (the supposed types of this species) in the 

 Museum of the Geological Survey at Ottawa, which should rather be classed with 

 Bathyuriscus, Meek. 



Sec. IV., 1899. 6 



