118 ROYAL SOCIETY OF CANADA 



This operculum has the venti-al limb sharply upturned at about a rii^ht 

 angle and has the nucleus about one quarter of the width from the 

 ventral side ; froju the nucleus two grooves s])read toward the lateral 

 edges, widening as they go ; in front of the nucleus and of these grooves 

 is a subtriangular elevated area, extending to the margin on the dorsal 

 side. On the external surface of the operculum obscure concentric Hnes 

 of growth are visible with a lens. The length of the operculum is 5 ram., 

 and the width 4 mm. 



JIyoi.ithes Ri'uosi-8 (PI. VII.. tigs. 4rt and b). 

 Hyolitkesruyosvs, Silt. Hist. Soc. \.B., Bull, xviii., pi. iii., p. 194, figs. 4« and 6. 



A small slender ei^ecies having the dorsal side flatly rounded trans- 

 versely ; and having a gentle, convex curve lengthwise. The taper of the 

 tube is about 1 to 3, and the apical angle about 15°. The tube is cham- 

 bered about 3 mm. from the apex. 



Sculpture. — The ventral side is marked by prominent ribs which are 

 closely set on the lower pact of the tube (about 6 to 1 mm.), but in the 

 upper fifth are more distant (2è to 1 mm). The whole surface carries a 

 minute granulation. The dorsal surface is unknown. 



Size. — Length 11 mm. Width about 3^ mm. Depth from dorsal to 

 ventral side 2 mm. Infrequent. 



Mr. Walcott described an object similar to this, but of onl}- half the 

 length (HyoUthellus micans var. rugosa) from several localities in the 

 Cambrian slates of Washington County, N.Y. It differs in having a 

 longitudinal striation between the transverse ridges, where this species 

 has a granulated surface. 



APTYCHOPSIS, Barrande. 



Among the rarer fossils of the Smith Sound limestone are a few 

 valves of crustaceans that appear to belong to the above genus, or an 

 allied one. 



Aptyoiiopsi.s terranovicus (PI. VII., fig. 5). 



Apfychopsis terranovicus, Nat. Hist. Soc. N.B., Bull xviii., p. 1!I5, pi. iii., fig. 5. 



Only the right valve known ; this is oval lenticular in shape, the 

 widest part being one third from the anterior end. The hinge-line has a 

 strong fold which is more than two thirds of the whole length of the 

 shield. From the front of the hinge-line the border runs with a slightly 

 convex arch to the anterior end. At about the middle of this part of the 



