Emarginula. 



MOLLUSCA. 



103 



4. PiLEOPSis TRILOBUS. — The Three-lobed Pileopsis, pi. 

 XLVII. fig. 50 and 55. 



Pileopsis? trilohus. Phillips, II. p. 224, pi. 14, fig. 12, 13. 



Subconic, smooth, arcuated from the base to the vertex, 

 which is straight, gradually tapering and acute at the vertex, 

 pointing downwards, and nearly reaching the margin ; aperture 

 trilobate ; base taking the undulous character of the lobes. 



Mountain Limestone of BoUand. 



5. Pileopsis tubifeb. — The Tubed Pileopsis, pi. XLVII. 

 fig. 52. 



Pileopsis tuhifer. Sowerby, VI. p. 224, pi. 607, fig. 4. 

 PhiUips, IL p. 224, pi. 14, fig. 14. 



Elongated, smooth, narrow, arcuated ; vertex but slightly 

 curved ; three obscure, divergent, spinous ridges emanating 

 near the vertex, and terminating on the margin, with three 

 rows of long tubular spines, extending upwards of half an inch 

 beyond the margin. 



Mountain Limestone, BoUand, and near Preston. 



6. Pileopsis vetustus. — The Ancient Pileopsis, pi. 

 XLVn. fig. 53. 



Pileopsis vetusta. Sowerby, VL p. 223, pi. 607, fig. 1, 2, 3. 

 Phillips, II. p. 224, pi. 14, fig. 19 ? 



Subconical, considerably arcuated, smooth; vertex blunt, and 

 slightly bent ; posteriorly contracted, and compressed on the 

 sides ; each with two or three irregular undulations, crossed by 

 nearly obsolete, waved lines of growth ; aperture oblong-ovate, 

 broadest in front, the margin sinuous, conforming to the undu- 

 lations. 



Mountain Limestone, Queen's County, Ireland, Preston, and 

 at Bolland. 



7. Pileopsis angustus The Straitened Pileopsis, pi. 



XLVIL fig. 54. 



Pileopsis angustus. Phillips, II. p. 224, pi. 14, fig. 20. 



Subconic, spiral, smooth, narrow above; vertex turned to one 

 side, obtuse ; with transverse, wide-set lines of growth ; aper- 

 ture elongated, and expanded behind. 



Mountain Limestone, Bolland. 



Genus VL— FISSURELLA.— ^ra^wzeVe. 



Shell oblong, shield-shaped, or conically depressed ; 

 concave within ; destitute of spiral convolutions ; with 

 the vertex perforated, and directed towards the front of 

 the shell, the perforation subovate in some species, and 

 nearly round in others; margin of the shell thickened 

 around the inside, and generally crenulated ; muscular 

 impression visible near the inner edge, all round, widest 

 on the sides near the front; outer surface striated, 

 grooved, or radiated, from the vertex to the margin, and 

 generally decussated by lines of growth. 



1. FissuRELLA Gb^ca The Greek Fissurella, pi. 



XLVIII. fig. 7, 8. 



Fissurella Graca. Sowerby, V. p. 132, pi. 483. Fleming, 

 p. 365. Patella Graca, Brocchi, II. p. 259. 



Oblong-ovate, convex, somewhat longitudinally arcuated, per- 

 foration oval ; whole surface with many small ribs, radiating 

 from the apex to the base, composed of sets, consisting of one 



large and two small ones, and between each set is a still larger 

 rib ; these are intersected by numerous, transverse, elevated, 

 narrow thread-like ribs, which produce a thickening at their 

 intersections ; inside oblong-oval, smooth ; margin crenulated, 

 and a little arcuated. 

 The Crag at Ipswich. 



Genus VIL— SIPHO— jBro^rw. 



Shell ovate, subconic; vertex reflected, and slightly 

 spiral; with a small dorsal fissure situate near the vertex, 

 terminating internally by a rhombic, funnel-shaped sy- 

 phon, or cup, in some species, but devoid of it in others ; 

 base ovate ; exterior surface ribbed or striated. 



1. SiPHO CALTHUATA The Barred Sipho, pi. XLVIII. 



fig. 1,2. 



Emarginula ? s. Fissurella ? clathrata. Sowerby, VI. p. 

 33, pi. 519, fig. !• Fissurella clathrata, Fleming, p. 365. 



Prominently conical ; the vertex thick, and considerably in- 

 curved, reaching nearly to the base; whole surface with strong, 

 longitudinal, divergent ribs, emanating from the apex, and ter- 

 minating on the base, each of which project beyond the edge, 

 and form a crenulated margin, in the centre is a much thicker 

 rib, with an awl-shaped fissure, extending from the back of 

 the apex about half way down ; these ribs are crossed by 

 transverse ribs, which produce a beautifully reticulated aspect ; 

 aperture oval. 



The Oolite at Anchffe. 



Genus VIIL— EMARGINULA.— icrmarcA. 



Shell conical, shield-shaped; vertex inclined to the 

 posterior extremity; anterior margin with a notch, or 

 fissure ; internal cavity simple ; anterior sides of the mus- 

 cular impression interrupted, expanded, and not con- 

 tinued across the front. 



1. Emarginula reticulata — The Reticulated Emar- 

 ginula, pi. XLVin. fig. 3, 4. 



Emarginula reticulata. Sowerby, I. p. 74, pi. 33, lower 

 figures. Fleming, p. 365. 



Greatly conical, elongated ; vertex elevated, slightly turned 

 to one side, but not acute ; surface with twenty-four, or more, 

 strong, divergent ribs, crossed by numerous thread-like stria?, 

 which produce a fine reticulated appearance ; fissure short ; 

 aperture oval ; inside smooth. 



From the Crag, Holywells. 



2. Emarginula scarlaris. — The Ladder-like Emarginula, 

 pi. XLVIII. fig. 5, 5,* 6. 



Emarginula scalaris. Sowerby, VI. p. 34, pi. 519, fig- 3. 

 Fleming, p. 366. 



Conical ; vertex but very slightly bent, somewhat eccentric, 

 and obtuse ; with many divergent, equal ribs, the central one 

 cleft by the marginal fissure, the intervals crossed by very fine 

 stria;; aperture obovate. Diameter a little more than an eighth 

 of an inch. Fig. 5,* natural size. 



Found in the Oolite at Ancliffe. 



