18 Tate — List of Irish Liassic Fossils. 



cancellated by very fine oblique striae. Siphonal band very narrow, occupying 

 a slight depression on the upper carina, ornamented with three longitudinal 

 striae. Base imperforate, concentrically striated ; aperture subquadrangular. 



Dimensions. — Total length, "9 inch ; breadth of last whorl, '6 inch ; height 

 of last whorl, - 4 inch. 



P. Tectaria cannot be confounded with any Liassic species of the genus, 

 though related to P. subtilis, Deslong. It resembles in figure, several Palaeozoic 

 forms, and especially P. tornatilis, Phil., from the Carboniferous Limestone. 



Geological Position. — Zone of A. angulatus, between Garron Point and 

 Red Bay, two examples/./?. T. ) ; Island Magee, one example (S. A. Stewart). 



12. — HlNNITES ANGULARIS, 710V. spec., Plate I. fig. 2. 



Shell inequivale, subinaequilateral, thick, left valve convex, transversely 

 oblong; umbo subacute, not extending beyond the hinge line, which is moderately- 

 arched; ornamented with crowded radiating ribs, unequal, obtuse, the surface 

 of which is raised into spinous squamae, and alternating irregularly with smaller 

 and similarly ornamented costae; costae of umbonal region without spinous 

 nodulations. Five or six of the radiating costae are much stronger than the 

 others, and somewhat regularly disposed, giving a polygonal outline to the 

 valve. Ears ornamented as the rest of the shell. Right valve ornamented 

 as the other valve. Breadth 2 - 5 inches, length 2 inches. 



H. angularis agrees with Lima nodulosa, Terq., in the radiating spiniferous 

 ribs, alternately large and small; but differs in the absence of rugous, serrated 

 concentric striae, and in its greater gibbosity, oblong figure, inequivalve character, 

 and by the polygonal outline given to it by the larger ribs. 



Geological Position. — Zone of "A. angulatus,'' 1 Island Magee, two ex- 

 amples (R. T. ) ; lowest beds of Lower Lias, Laleston, S. Wales. (R. Etheridge), 

 Coll. Brit. Museum. 



13. — Avicula Pattersoni, nov. spec, Plate I. fig. 10. 



Shell depressed, ovate, transverse, slightly oblique, concentrically striated; 

 anterior margin arched, and superiorly sinuated; hinge line straight; anterior 

 wing very short, acute; posterior wing elongated, acuminated, excavated behind. 



A. Pattersoni has a general resemblance to Gervillia crenatula, Quenst., 

 which the author states distinctly to possess cardinal pits, and as the type 

 specimen of this species displays a single extended cartilage pit, it cannot be 

 referred to that genus. It has much analogy with A. Deshayesi, Terqm., but 

 is much less oblique, has a smaller anterior wing, and an acute umbo, not being 

 so concave a shell as that species. This species was referred by Portlock to 

 A. Goldfussi. Several specimens from Craig and Gortmore form part of the 

 Portlockian collection. The figured specimen I obtained from the Zone of 

 "A. angulatus" at Island Magee. 



The species is dedicated to my kind friend Robert Patterson, Esq., F.R.S. 



