THE FAUNA OF THE ST. JOHN GROUP. 39 



seulptnriug- ou the surface of the shell, visible only with a powerful leus, which is not a 

 regular granulation, but an irregular roughing of the surface. All the markings are most 

 distinct on the outer third of the valves. 



This interesting little species is referred provisionally to Acwlreta as the nearest 

 "•enus ; but there seem to be radical diiferences ( if the cast of a ventral valve above des- 

 cribed is of this species) in the internal markings, and there are features which remind one 

 both of Dùrina and Ortliis. The species also has a general resemblance to Acrothele coriacea 

 (Linnarsson) of the Swedish Cambrian rocks, especially in the dorsal valve.' This is the 

 shell which was referred to by the author iu Bulletin IV of the Natural History Society 

 of New Brunswick, St. John, as a Scenella, but on investigation it proved to be a Bra- 

 chiopod. 



Lenglh, 3| mm. Width, 3J mm. 



Horizon and Localiti/. In the fine, grey shales of Div. l.r, at Portland, N.B. Scarce. 



Found by W. D. Matthew. 



ACROTHELE, Linnarsson. 



Acrothele Matthewi, Hartt, sp. (Plate V. Figs, lô and 15«.) 



Lingula Maltliewi, Hartt. Acad. Geol., 2nd Ed., p. 644, Fig. 221. 



Acrothele Mattheivi, Hartt, sp. U.S. Geol. Surv., Bull. 10, p. 15. PI. I. Fig. 4, 4a. 



Professor Hartt described the dorsal valve, the only part known to him, in the follow- 

 ing terms : — " Circular in outline or A'cry slightly wider than long, extremely flat, the 

 convexity being scarcely noticeable; shell very thin; on each side a segment, such as 

 would be cut off by a cord running from the umbo to the extremity of the transvei'se 

 diameter, is slightly turned up on the margin. — Inside, a strong mesian ridge, rounded, 

 and of moderate width, runs from the umbo to a point a little beyond the middle of the 

 shell ; at the umbo, this ridge bears a small nail-like process or swelling, and there are 

 two minute and extremely short secondary ridges, originating from the head of the pri- 

 mary, and extending obliquely backwards. Inner surface marked with numerous indi.s- 

 tinct and irregular concentric striae ; outer surface not visible." 



Professor Hartt's example was a flattened shell ; as the dorsal valve, when not distorted 

 by pressirre, is convex, being strongly arched from hinge to front. 



The following additions may be made to his description of the species : — Width about 

 one sixth greater than the length. Hinge line about one fifth of the length of the trans- 

 verse diameter. Ventral valve elevated and subconical in the posterior half, flattened or 

 with margin reflected in the anterior and lateral slopes. 



The dorsal valve has the following internal features in addition to those mentioned by 

 Professor Hartt. The median ridge is accentuated by a minute tubercle scarcely half way 

 from the hinge line to the front, but extends beyond this point, becoming fainter, to 

 within one c[uarter of the longitudinal diameter, from the front : the two diverging lateral 

 ridges, which broaden the mesian ridge in its posterior part, extend opposite the minute 



' Compare the central scar and two niiiuite pits in tigure of tbat sjjecies, in Bracliiopoda of Paradoxide.s bods 

 of Sweden., pp. 22, 23. PI. iv. Fig. 43 6. 



