142 BRITISH CARBONIFEROUS BRACHIOPODA. 



contiguous or separated by sulci or interspaces of variable width. At irregular distances 

 the striae give rise to a few short, cylindrical, hollow spines, which are more numerous 

 upon the auriculate portions of the valve. Dorsal valve thin, concave, following the curves 

 of the opposite one, and similarly sculptured, the visceral portion and ears being also some- 

 times concentrically wrinkled, while the entire surface is crossed by minute concentric lines 

 of growth. In the interior of the ventral valve the divaricator muscular scars are imme- 

 diately under and outside of the adductor or occlusor ones, and lower down towards the 

 centre of the valves there are two deep subspiral depressions. In the interior of the dorsal 

 valve the cardinal process is trilobed and V shaped, under which a narrow longitudinal 

 ridge extends to about half the length of the valve, and on either side are situated the 

 ramified dendritic impressions of the adductor or occlusor muscle, while outside and in 

 front of these are the two " reniform impressions." The internal surface is covered with 

 innumerable asperities, and the shell structure perforated by canals. Dimensions variable, 

 four British examples measured — 



Length inches 2 lines, width 1 1 inches 6 lines. 



3 3 " 3 3 " 3 3 3 3 " 3 3 " 3 3 



33 ^ 33 « 33 33 " 33 •'•'J 33 



33 W }> " 33 33 ' 33 ** 33 



06s. Of the many species of which the genus Proditctt/s is composed, this is certainly 

 the largest and most remarkable, some examples having attained eight inches in length by 

 twelve in breadth, but it is also most variable in its shape, so much so, indeed, that one 

 is at times seriously puzzled, and tempted to fabricate more than one so-termed species 

 out of its variations. The shell has been several times minutely described since its first 

 discovery, but Palaeontologists are far from unanimous with reference to some of its sup- 

 posed synonyms. Martin's figure of Anomites giganteus represents the adult typical shape 

 of the species, with its developed auriculate expansions, while the same author's A. crassus 

 illustrates an adult individual of the same, but in which the ears are broken or undeveloped, 

 and it is quite easy to find in the same quarry and bed specimens graduating from the one 

 into the other. In one, Plate XXXVIII, is represented, of the natural size, a very remarkable 

 example of the typical form, with unusually expanded ears, while in Plate XXXIX (fig. 3) 

 will be found a reduced illustration of a still more circular specimen than that upon which 

 Martin's P. crassus was founded. The greater number of Palaeontologists have considered 

 P. kemisjj/iaricus a synonym of P. giganteus, and I am inclined to believe that they are 

 substantially correct, but it must be remembered that in this case the name has been, at any 

 rate, applied to two conditions of the species. James Sowerby's original illustrations in Tab. 

 328 of the ' Mineral Conchology/ which we consider the typical ones, appear to represent 

 what I take to be a local modification, which had better be described separately with the 

 varietal designation " /u>j//iy)/taricus," while the figures of P. hemi&pharicm in Tab. 561 

 of the same work, published some five years later by Mr. J. de C. Sowerby, represent the true 

 adult condition of that shape of P. giganteus to which Martin had applied the denomination 



