28 BULLETIN OF THE 



growth, a moderate distance apart, and distinct. The interior cast of the 

 dorsal valve is in general moderately convex, at the edges heing more finely 

 and less distinctly striate than the exterior surface. The margin along the 

 beak is flat. The cardinal scars in the cast follow the outline of the shell, and 

 are well defined along their exterior outline, but not along their interior. The 

 reverse is true of the casts of the lateral scars. The lateral scars unite with 

 the central scars, forming a figure comparable with that of a reversed W, 

 which is distinctly outlined along the outline facing away from the beak, but 

 is indistinct along the outline facing the cardinal scars. The diameter of the 

 shell is 5 mm. 



Locality and position. — Station No. 2, North Attleborough, Mass., Cam- 

 brian, one specimen. 



3. Fordilla (Troyensis, Barrande?). 



Plate I. Fig. 4. 



Cast of left valve 7 mm. long and 4 mm. broad, moderately convex along the 

 border, quite strongly convex near the hinge line. The broadest part of the 

 shell is slightly anterior to the middle of the length of the shell. Posteriorly 

 the shell decreases rapidly in breadth. The posterior extremity is rounded, 

 but more attenuate than in specimens figured by Walcott. Anteriorly the 

 border of the cast is narrowly indented; in consequence of the indentation, 

 the border is produced as a small lobe, and forms the anterior extremity of the 

 shell. A rather broad, shallow groove runs along the shell near the margin. 

 The cast shows no striae. 



Compared with typical specimens of this species, the North Attleborough form 

 is largei', more attenuate posteriorly, and more strongly arched near the hinge 

 line. Walcott, in his Second Contribution to Cambrian Faunas,* figures, on 

 Plate XI. fig. 3 b, a cast which forms a connecting link between the form 

 here described and the typical forms, which have a broader posterior outline. 



Locality and position. — Station No. 1, North Attleborough, Mass., Cambrian, 

 one specimen; also at Troy and Schodack Landing, N. Y. 



4. Lamellibranch ? 



Plate I. Fig. 5. 



A single specimen of entirely unknown relations has at least the genei'al 

 outline of a Lamellibranch. It is 9.5 mm. long and 3.7 mm. wide. The 

 border is gently curved ; the hinge line almost straight. Along the hinge line 

 is a flat, strongly inclined narrow field, with fine striaj almost perpendicular 

 to the hinge line. The rest of the shell forms a surface almost perpendicular 

 to the hinge area. It is finely striated, the curved strise following the outline 

 of the border. The broadest part of the shell is about one third the dis- 



* Bulletin U. S. Geol. Survey, No. 30. 



