Pinna. 
CONCHIFERA. 
169 
right baud valve than in the opposite ; the interior pearlaceous 
substance of tlie shell is spread out almost in the same form as 
the exterior fibrous and more extended portion ; one distinct, 
somewhat oblique and irregular muscular impression, and a 
series of small dots, are placed at the posterior side, near the 
sinus for the byssus, which answer as points of attachment for 
a part of the mantle. 
1. Pkrna alasformis. —The Wing-shaped Perna, pi. 
LXXI. fig. 20. 
Modiola (?) alteformis. Sowerby III. p. 93, pi. 2,51. 
Triangular; length nearly twice its breadth, producing a 
wing-like appearance; ventricose; anterior lobe somewhat 
compressed ; posterior lobe very small; back parallel; disk 
convex; beaks produced, between one and the other a con¬ 
cave space intervenes ; surface rough and somewhat imbricat¬ 
ed ; thickness of the united valves equal to the width of the 
shell. 
The Lower Greensand, Court- at-Street. 
2. Perna mytiloides. —The Mytilus-formed Perna, pi. 
LXVII. figs. 1, 2. 
P. mytiloides. Phillips, Geo. York, I. pi. 9, fig. 21. 
Mytiliform, elongated; posteriorly incurved; hinge-line 
slightly curved and considerably oblique ; ligamentary grooves, 
seven or eight, elongated ; beaks rather obtuse, pointing pos¬ 
teriorly ; surface smooth, with shallow, concentric Hues of 
growth. 
The Cornbrash, Bullwick ; the Great Oolite, White Nab, 
Cloughton Wyke, and the Inferior Oolite, Cheltenham. 
3. Perna quadrata. — The Squarish Perna, pi. LXIX. 
fig. 11. 
P. quadrata. Sowerby, V. p. 149, pi. 492. 
Elongated, somewhat square; valves with one side shorter 
than the other, gibbose and unequal ; hinge-line a little 
curved ; the cartilage pits large and few ; beak rather pointed, 
that of the larger valve prominent, the other somewhat shorter ; 
surface smooth, with a few indistinct, shallow lines of growth. 
The Portland Stone, Swindon and Garsington. 
4. Perna rostrata. — The Beaked Perna, pi. LXIX. figs. 
14, 15. 
P. rostrata . Sowerby, Geo. Tr. 2d Ser. IV. p. 342, pi. 17, 
fig. 17. 
Ovate, compressed; hinge-line straight and horizontal ; 
lesser wing produced and w'ell defined ; base rounded ; beaks 
rather obtuse and not protruding; substance of tho shell thin. 
In tho Greensand, Blackdown. 
5. Perna rugosa. —The Rugged Perna, pi. LXI.*** f. 3. 
P. rugosa . Goldfuss, pi. 108, fig. 2. 
Sub-quadrate; hinge-line lengthened, oblique; area with 
eighteen or nineteen oblong parallel grooves; beaks acute, con¬ 
siderably turned to one side, with a lunular excavation under 
them ; surface with many irregular, raised, concentric rough 
lines of growth. 
The Great Oolite, Scarborough. 
Triue II.—MYTILACEA. 
Hinge with tho ligament sub-anterior, marginal, linear, 
very entire, occupying a great portion of the anterior bor¬ 
der ; shell rather foliaceous. 
Genus XXX11.—PI NX A.—j Linnaeus. 
Shell equivalve, longitudinal, oblique, wedge-shaped; beak- 
forming an elongated point; posterior side generally trun¬ 
cated, and always gaping; the anterior margin nearly a 
straight line, and a little open in the centre for the passage 
ol the byssus; hinge without teeth; ligament margin greatly 
lengthened and linear; ligament partly internal, and continu¬ 
ing along tho whole dorsal margin; two muscular im¬ 
pressions in each valve, the posterior one very large, almost 
central, tho anterior one terminal, and sometimes double; 
muscular impressions of the mantle destitute of a sinus. 
1. Pinna ampla. —The Spacious Pinna, pi. LXXI. 
fig. 19. 
Mytilus ampins. Sowerby, I. p. 27, pi. 7. 
Triangular, compressed; posterior side straight, slightly 
undulous ; base gradually curved to tho back ; length 
nearly twico its breadth, somewhat compressed ; surface with 
rather wide, longitudinal, undulating stria,*, which proceed from 
the beaks and back near to the base, the posterior side not 
striated ; substance of tho shell thin. 
The Great Oolite, Bath and Malton, and the Inferior 
Oolite, Somersetshire and Yorkshire. 
2. Pinna flabelliformis. —Tho Fan-shaped Pinna, pi. 
LXVII. fig. 19. 
P. costata. Phillips, Geo. York, II. p. 211, pi. 6‘, fig. 2. 
Much elongated, narrow, nearly straight; beaks acute, mid¬ 
dle of the valves with many longitudinal, narrow, deep 
grooves, crossed by remote, concentric lines of growth ; to¬ 
wards tho beaks the valves are destitute of grooves. 
Tho Carboniferous Limestone, Ashford, Bakewell, Bo¬ 
land and Moulton. 
3. Pinna gracilis. —The Slender Pinna, pi. LXIX. 
fig. 12. 
P. gracilis. Phillips, Geo. York, I. pi. 2, fig. 22. 
Much elongated, slender, slightly arcuated ; beaks rather 
obtuse; anterior side with longitudinal shallow furrows ; 
and remote, shallow, transverse lines of growth. 
Tho Specten Clay, Speeton, Yorkshire. 
4. Pinna lanceolata.— The Spear-shaped Pinna, pi. 
LXIX. fig. 10. 
P. lanceolata. Sowerby, III. p. 145, pi. 281. 
Lanceolate, much elongated, its length being equal to four 
times its breadth; and a little arcuated, section quadran¬ 
gular ; each valve being divided into two flat sub-triangular 
parts by a mesial line; surface with some longitudinal wide- 
set strise at the beaks, and extending downwards for some 
inches, with transverse, shallow wrinkles. 
The Coral Rag, Scarborough, Malton, and Magilligan, 
Ireland. 
5. Pinna inflata.— The Inflated Pinna, pi. LXVII. 
fig. 12. 
P. injlata . Phillips, Geo. York, II. p. 211, pi. 6, fig. 1. 
Conical, inflated ; beaks nearly central; surface with many 
small, elose-set, equal furrows. 
The Carboniferous Limestone, Bolland, Yorkshire. 
6. Pinna cuneata. —The AVedge-shaped Pinna, pi. LXIX. 
fig. 13. 
P. cuneata. Phillips, Geo. York, I. pi. 9, fig. 17. 
2 Q 
