604 THE UPPER SILURIAN. 



convex, scarcely gibbous ; umbonial slope regularly convex, below 

 which is a slight depression reaching to the postero-basal margin ; 

 posterior end rounded, the longer part of the curve on the basal side. 

 Anterior end short and nari'ow, somewhat abruptly rounded. Surface 

 marked by regularly radiating rounded striae with faint concentric lines 

 of growth. 



This differs from the preceding species in being less gibbous, in the 

 more nearly parallel cardinal and basal lines in the direction of the 

 umbonial ridge, and in the stronger radiating striae. Arisaig, East 

 River, coll. J. W. D. 



Avicula Honeymani, Hall (Fig. 210). Left valve : body of the 

 shell obliquely ovate, convex and somewhat gibbous towards the 

 umbo, anterior wing small rounded, posterior wing large triangular, 

 obtuse at the extremity, extending two-thirds the length of the shell. 

 The line between the wing and body of the shell well defined by a 



Fig. 210. — Aficula Honeymani. 



slight abrupt depression along the junction. Surface marked by 

 rounded radiating stri« which are interrupted by fainter concentric 

 undulations or lines of growth ; the wing is marked only by con- 

 centric strife. 



This species bears some resemblance to A. emacerata of the Niagara 

 and Clinton groups of New York ; but its form is slightly more oblique, 

 and the wing is marked only by concentric strife, while in the New 

 York species the radiating lines on this part are stronger than the 

 concentric ones. Arisaig, coll. J. W. D. 



Grammysia triangidata, Salter. Arisaig, Dr Honeyman. 



Grammysia cingulata, Hisinger. Arisaig, Dr Honeyman. 



Pterinea retroflexa. Arisaig, Dr Honeyman. 



Goniophora cymlaeformis^ Sow. Arisaig, Dr Honeyman. This 

 and the three last shells I give on the authority of Dr Honeyman 

 and Mr Salter. 



Theca Forbesii, Sharpe. Collected by Dr Honeyman at Arisaig. 



Murchisonia Arisaigensis, Hall. Shell teretely conical, volutions 

 about five, gradually increasing from the apex, rounded with a slight 

 angulation or carina in the middle. The surface is unknown, and the 



