34 G. F. MAÏTIIEW : ILLUSTEATIONS OF 



long ; it is more inflated than the ventral valve, and diflers from it in being decidedly 

 arched from the beak to the front. 



These characters, however, do not fully represent the species, which shows qiiite 

 important variation in the adult forms. In the ventral valve, the beak is more attenuated 

 in the mature shell and the front more squarely rounded, the extreme width of the shell 

 at that age being about one third from the front, which is very gently curved. 



The dorsal valve in the adult exhibits a corresponding change in outline, the widest 

 part being nearer to the front than to the umbo. In both valves the shell slopes gently 

 on both sides and in front, to the margin. The ventral valve is flatter than the dorsal, and 

 not arched at the margin, between beak and front, like the latter. 



S(iilj)lure. as described in Mr. Walcott's bulletin. There are about eight or ten con- 

 centric strioe that are more distinct than the others ; within these, near the umbo, is a 

 thickened, glossy, elevated portion of the shell. 



This species when half grown may be compared to LinguleUu femiginea of the Welsh 

 Cambrian, but in its adult stage approaches somewhat to the form of a true Lingula; the 

 following changes of form in the ventral valve of young, medium-sized and adult speci- 

 mens has been observed :■ — At 2i mm., length and breadth nearly equal ; at 3J mm., length 

 one fifth greater than width ; at 6 mm., length one half greater than width. 



The author has dedicated this species to Sir William Dawson, who has done so much 

 to make known the ancient fauna of St. John group by his publication in the " Acadian 

 Geology" of the forms first observed in this formation. 



Length, 6 mm. Width, 4J mm. 



Horizon and Lo)-(tJibj. Found at Portland, N.B., at Ilatclill' Stream, Simonds, and at 

 Hanford Brook, St. Martin's, chieliy in the grey shales of Div. I.e. The young or a dwarf 

 variety has been observed in tlie dark grey shales of DIa'. \.d, at Porter's Brook, St. Martin's. 



LiNGULELLA TJXGULOIDES, n. sp. (Plate V. Figs. 8, 8rt and b.) 



Ovately elliptical, one half longer than wide. 



Dorsal valve almost regularly elliptical, slightly produced at the umbo, which is 

 moderately elevated; the more tumid part of the valve is wider than that of the ventral, 

 and extends about haU-way to the front. 



Ventral valve subattenuate at the umbo, which is rather prominent ; central half of 

 the valve markedly elevated above the sides for nearly its whole length, and more tumid 

 than the dorsal valve. 



Sculpture. Surface marked by numerous sharp concentric stri;e, of which about six or 

 seven placed at regular intervals, are more distinct than the others. More faintly marked 

 radiating striie can also be traced on the surface of the shell, especially towards the margin. 



This little species is about the size oï Lingulella ferruginea (Salter), biit it differs in its 

 comparatively greater length, and in the elliptical outline of its valves. It differs from 

 the Acadian species last described in its greater comparative length, in its tumid ventral 

 valve, etc. 



Length, 4 mm. Width, 2i mm. 



Lomlily and Horizon. In the fine dark shales of Div. I.c/, at Porter's Brook, St. Martin's. 

 Rare. 



