LiNGXJLA. 



MOLLUSCA. 



107 



The Mountain Limestone, Northumberland. 



9. LiNGULA TRUNCATA. — The Truncated Lingula, pi. LIII. 



fig. 4. 



Lingula truncata. Sowerby, Geo. Trans. IV. 2nd series, p. 

 339, pl. 14, fig. 15. 



Ovate, smooth, longitudinally compressed, most so in the 

 centre of the valves ; base parallel. 



Lower Greensand, Kent. 



10. Lingula cornea The Horny Lingula, pl. XLIX.* 



fig. 1. 



Lingula cornea. Murchison, Sil. Syst. p. G03, pl. 3, fig. 3. 



Oblong; umbonal region subacute, gradually widening to- 

 wards the centre, from whence the sides are nearly parallel ; 

 base very slightly rounded, or nearly flat. 



Lowest beds of the Old Red Sandstone. 



11. Lingula minima The Very Small Lingula, pl. 



XLIX.* fig. 2. 



Lingula minima. Murchison, Sil. Syst. p. 612, pl. 5, fig. 23. 



Oblong, somewhat elongated ; beaks subacute ; flat, smooth, 

 and thin, with parallel sides, a little broader below than above ; 

 base but slightly rounded. Length four lines ; width two lines 

 and a half. 



Found in the Upper Ludlow Rock at Dowton Castle and 

 Delbury. 



12. Lingula lata The Broad Lingula, pl. XLIX.* fig. 3. 



Lingula lata. Murchison, Sil. Syst. p. 618, pl. 8, fig. 11. 

 Obovate; beaks rather produced; flat, smooth; sides and base 



rather rounded. Length three lines; breadth about two lines. 

 Lower Ludlow Rock, in escarpments, at Evenhay, Elton, &c. 



13. Lingula striata The Striated Lingula, pl. XLIX.* 



fig. 4. 



Lingula ? striata. Murchison, Sil. Syst. p. 619, pl. 8, fig. 12. 



Obovate, very much compressed, somewhat quadrangular; 

 beaks but slightly developed ; base nearly parallel ; whole sur- 

 face with minute, transverse striae. Length five lines ; breadth 

 four lines. 



Lower Ludlow Rock near Amestry. 



14. Lingula attenuata The Attenuated Lingula, pl. 



XLIX.* fig. 5. 



Lingula attenuata. Murchison, p. 641, pl. 22, fig. 13. 



Elongated, compressed, smooth, acuminated above, wide be- 

 low; beaks prominent and acute; sides rather flat above, some- 

 what rounded below ; and the base slightly arcuated. Length 

 seven lines and a half; breadth five lines. 



Lower Silurian Rocks, Golden Grove, Caermarthenshire ; 

 Meadow Town and Rorington, Salop. 



15. Lingula Levvisii. — Lewis's Lingula, pl. XLIX.* fig. 6. 

 Lingula Lewisii. Murchison, p. 615 and 631, pl. 6, fig. 9. 

 Oblong, compressed, smooth; beaks very obtuse; a little flat 



above, and somewhat produced below ; sides parallel. Length 

 one inch and two lines ; breadth nine lines and a half. 



Common in the Silurian Rocks, of which it is highly charac- 

 teristic; the Amestry Limestone, Ludlow promontory; at Mary 

 Knoll; Palmer's Cairn; and Sunny Bank: it also occurs in the 

 Wenlock Shale at Tynewydd, Wenlock, and Buildbwas. 



16. Lingula? truncata The Truncated Lingula, pl. 



XLIX.* fig. 7. 



Lingula truncata. Sowerby, Geo. Trans. IV. 2nd series, p. 

 339, pl. 14, fig. 15. 



Ovate, compressed ; beaks hardly elevated above the body ; 

 sides nearly parallel ; base straight. 

 Lower Greensand, Kent. 



Genus II CRANIA. — Retzius. 



Shell inequivalve, suborbicular, mostly equilateral, 

 slightly irregular ; upper valve patelliform, very convex, 

 interiorly provided with two projecting callosities, its 

 umbo placed rather behind the centre; lower valve adhe- 

 rent, nearly flat, pierced on its end or surface with three 

 unequal or oblique holes ; each valve with four muscular 

 impressions ; two of those in the upper valve are situate 

 near the posterior margin, the other nearer the centre, 

 but always close to each other ; in the lower valve two 

 are almost marginal, and remote, but the other two are 

 nearly central, and so close together that they seem 

 united, with usually a small projection between them ; 

 destitute of a hinge. 



1. Crania Parisiensis. — The Parisian Crania, pl. LIII. 

 fig. 1, 2, 3, 4. 



Crania Parisiensis. De France, Diet, des Sci. Nat. La- 

 marck, VI, pt. 1st, p. 259- Cuvier and Brongniarte, Geo. des 

 Env. de Paris, Ed. 1822, p. 15, pl. 3, fig. 2. Sowerby, V. p. 3, 

 pl. 408. Criopus Parisiensis, Fleming, p. 377. 



Suborbicular, compressed ; upper valve thin, smooth in the 

 centre, with obscure, granulated, irregular spines round the 

 edges ; its umbo small, acute, and placed a little to one side ; 

 margin folding over, and descending beyond the elevated edge 

 of the lower valve ; lower valve thick, with a considerably 

 elevated margin, and cellular in its structure, a few nearly obso- 

 lete, divergent stria? upon its inner surface, and attached by its 

 whole outer surface ; muscular impressions variable, sometimes 

 exceedingly indistinct, and at others very deep ; the elevation 

 between the central ones also varies, being sometimes elevated 

 along with it, in which case it has a strong resemblance to the 

 human cranium. 



Found attached to fragments of the shells of Catillus, &c., in 

 the Chalk, particularly that of Norfolk. 



Genus III._SPIRIFER.— ^'ott-ez-Jy. 



Shell transverse, equilateral, inequivalve; hinge 

 straight, linear, widely extended equally on both sides 

 of the umbones, which are more or less remote, being 

 separated by an intermediate flattened area, varying con- 

 siderably in breadth in different species, and consists of 

 three triangular parts, a central and two lateral ones; 

 this area is divided in the centre by a triangular pit, for 

 the passage of a byssus ; within the smaller valve, and 

 near the umbo, two spiral testaceous appendages are 

 attached, whose convolutions diminish in size as they 

 diverge from the centre of the shell. 



