428 BRITISH PALALOZOIC FOSSILS. [Bracutoropa. 
towards the margin of large specimens; anterior half of each ridge fringed with rather coarse notches (about 
fifteen in the space of two lines), scarcely visible without the lens, from which slight radiating strice extend 
across the posterior half ; when decorticated, slender, radiating lines make their appearance, Average width two 
68 
inches, pevemens length of receiving valve =, of entering valve 3, height of cardinal area 33, width of 
109 
hinge line “, width of sinus in front margin about ;3, height thereof about =, depth of entering valve 3%, of 
0 
receiving valve . Width of young specimen one inch one line, proportional length of receiving valve 7, 
length of entering valve =, height of area ,;,, depth of both valves 5. 
I agree with Mr Phillips in considering this quite a distinct species from the S. lineata with which 
M. de Koninck unites it ; at all ages and sizes it is more transverse, more depressed, the beaks are further apart, 
and above all, the species is distinguished by the sinus in the front margin and strong mesial hollow, extending 
to the apex of the beak. It is only when the shell is removed that the comparatively strong, radiating strize, 
figured by Phillips, are seen; the reticulation exactly resembles that of S. lineata. 
Position and Locality.—Not very uncommon in the lower carboniferous limestone of Kendal, Westmorelgnd. 
Sprrirera (Martinia) GLABRA (Mart. Sp.) 
Ref. and Syn. = Anomites glaber Martin, Pet. Derb. t. 48. f. 9, 10. = (8. glaber Sow. Min. Con. t. 269. f. 1. 
+8. obtusus id. id. f. 2.+ 8. oblatus id. id. t. 268.) 
Desc.—Transversely oval; hinge-line much shorter than the shell, sides and cardinal angles much, and 
regularly rounded; cardinal area moderate, variable, triangular; surface smooth, very finely fibrous under 
a strong lens; front margin raised into a sinus. 
There are three moderately distinct varieties, which however certainly pass into each other, viz. 
Var.a. GLABRA. 
Moderately depressed, varying considerably in width; mesial ridge (and hollow) rather narrow, round, 
or slightly flattened, distinctly marked nearly to the beak, sides rather depressed, beaks rather small, moderately 
approximate ; old specimens occasionally shewing a few obscure radiating ridges, about a line wide near the 
margin. Width of rather wide specimen two inches nine lines, Poopestioua length of receiving maker, a> length 
of oe valve =, length of SUIS ERE tm, Width of cardinal area ;;, depth of entering valve 4, of receiving 
valve 2%, width of sinus in front margin =, depth thereof =. 
Specimens of this variety occur commonly of less proportional width, and often with the mesial ridge and 
hollow becoming indistinct a considerable way from the beak, passing into the next variety. 
Var. B. OBLATA (Sov.) 
Ovato-rhomboidal, gibbous; sinus in the front margin wide, shallow, subquadrate, the ridge and hollow from 
which are indistinctly marked, and nearly disappears within an inch from the beak ; receiving valve with a very 
large tumid beak, much incurved, and approximating that oF the entering valve. Width of average specimen 
two inches two HES proportional length of receiving alien =, of coLerng walee 2 in» width of hinge line 3%, width 
of cardinal area ;4, width of sinus in front margin =>, depth thereof ;2, depth of entering valve im» depth of 
receiving valve =. 
The obtusely-rounded rhomboidal form, and evanescent mesial fold, and obtuse, approximate, beaks, dis- 
tinguish this variety from the true variety glabra, and more strongly still from the next variety. In some 
specimens much more gibbous, and in some much flatter than the above measurements from the Isle of Man, 
the cardinal area becomes almost obsolete, and the beaks very approximate. One specimen also shews the 
spiral appendages as large, or nearly so, as in the typical Spirifers. 
Var. y. OBTUSA (Sov.) 
Transversely oblong, very gibbous, sides tumid; sinus in the front margin very deep, as high as wide, 
rounded, angular, with a strongly raised narrow, rounded, mesial ridge extending nearly to the beak of the enter- 
