FAUNA OF THE ST. JOUN GKOUP. ^ 39 



BRYOaHAPTUS, Lapiuorlh. 



Bryograptus Kjerulfi. Lap. ? ' 



A graptolite which may belong to this species occurs with the earliest form of Dicty- 

 onema present iu the St. Johu basiu. 



Unfortunately the material obtained for this species is very fragmentary. It is, how- 

 ever, of such a nature that it cannot belong to a Dictyouema, as it consists of branches that 

 are wider than those of D. jlabellifurme, and are free from each other. 



The branches of the hydrosome are about 1 mm. wide, and there are from twelve to 

 thirteen"hydrothecœ in a space of 10 millimetres. 



Horizon and Locality. — In the black slates of Division 3 b, at Navy Island, St. John 

 Harbour. 



LiNGULELLA L^vis, n. sp. (PL XII, fig. 4 a and b.) 



A large oval-ovate species, with a very thin test, resembling a Liugula in its thin 

 hinge line, but having a pedicel groove. 



Sculpture. — The shell has a smooth, shining surface, but when observed with a lens 

 very fine concentric and fainter radiating lines are made visible. 



Size. — Ventral valve, length, 15 mm. ; width, 11 mm. Dorsal valve length, 14 mm. ; 

 width, 11 mm. Another dorsal is 17 mm. long and 15 mm. wide. 



Horizon and Localilij. — In dark grey slaty shales of Div. 8 a on the right shore below 

 the " Falls," St. John Harbour. 



Among Hall's species of the Potsdam sandstone of Wisconsin Lingnla aurora comes 

 nearest this, but is smaller. No British species of the Upper Cambrian appears to be 

 nearly related to it. 



OBOLELLA, Billings (1861). 



The following is Billings' definition of this genus : — " Shell ovate, circular or sub- 

 quadrate, convex or plano-convex. Ventral valve with a false area, which is sometimes 

 minute, and usually grooved for the passage of the peduncle. Dorsal valve either with 

 or without an area. Muscular impressions in the ventral valve four ; one pair in front of 

 the beak, near the middle or in the upper part of the shell, and the others situated one on 

 each side near the cardinal edge. Shell calcareous. Surface concentrically striated, 

 sometimes with thin, extended lamellose ridges. 



" In general form these shells somewhat resemble Obolus, but the arrangement of the 

 muscular impressions is different. In Obolus the two central scars have their smaller 

 extremities directed downwards, and converge towards each other ; but in this genus the 

 arrangement is exactly the reverse." 



The three species which Billings referred to this genus were O. chromatica from the 

 Potsdam Sandstone at the Straits of Belle Isle, O. crassa {^Avicula ? desquamafa Hall) of 

 the primordial limestone at Troy, N.Y., and O. polita of the Potsdam Sandstone of St. 

 Croix K., Minnesota. 



' Better material, collected since the article was written, enables me to say that this is not B. Kjerulfi. 



