126 

 Desoription of the species :— 



Class BRAOHIOPODA. 

 Order CLISTENTERATA. 



Family Spiriferid^. 



Gen'}iSi Atiypa, Dahnan, 1828. 



(K. Vet. Acad. Hand!., 1S27, p. 102.) 



Atrypa RKTicuLARis, Linn. 



A. TPficuJayis (Linii.\ Davidson, ^ion. Brit. Sil. Brachiopoda, 1867 

 Pt. ii., p. 129 (for synouomy), t. 14, f. 1 - 22. 

 Obs. — This protean species is numerously represented in the 

 Lilydale Limestone, Prof. Tate informs me. We have one 

 example. 



Class PELECYPODA. 



Order MYTILACEA. 



Family AvicULlDiE. 



Genus Ambonychia, Hall, 1847. 



(Pal. N. York, T., p. 163,) 



Ambonychia'? poststriata, sp. nov. 



(PI. xviii., figs. 1 and 2.) 



Sp. Char. — Shell deltoid, or trian£;ularly-mytiliform, alate 

 posteriorly, truncate anteriorly. Valves convex in the umbonal 

 region ; hinge line straight ; ventral margin convex, rounding fore 

 and aft insensibly into the anterior and posterior margins; anterior 

 alation wanting, the margin truncated, and somewhat incurved, 

 straight walled, and with a large, deeply excavated byssal notch, 

 cordate when the valves are in apposition ; posterior end alate, 

 more or less flattened, but no concavity along the posterior slope; 

 umbones sharp, prominent, and elevated above the hinge line, 

 slightly incurved ; body of the shell gently convex from the 

 umbones downwards to the ventral margin. Sculpture consisting 

 of coarse concentric lamina? of gi'owth, uncrossed by any radiating 

 or decussating strife, except on the posterior slope, which is finely 

 radiate, the intersection with the concentric lamina; giving rise to 

 a fine fimbriation. 



Obs. — The genus Ambonychia possesses two allies, Anomalodonta, 

 Miller, and Opisthoptera, Meek, greatly resembling it in external 

 appearance, but differing in the internal structure of the hinge, 

 and to eithei' of which the present species might equally well be 

 referred, but as we are quite ignorant of the characters of the 

 dorsal margin, I have thought it better to provisionally place the 

 shell in the genus in chief. It differs, however, from all three, in 



