The marine Carboniferous of Nortli-east Greenl. and its Bracliiopod Fauna. 577 



Of this characteristic form there is a specimen from the black 

 bituminous limestone with Spirifer supramosquensis, in the Conglo- 

 merate section {N:o 190). 



The specimen is complete, with the two valves attached to each 

 other, but the dorsal valve has been concealed by rock substance 

 which it has not been possible to entirely remove. In consequence 

 of its state of preservation, it has been impossible to discern among 

 the peculiar characteristics distinguishing the genus more than the 

 little deltidial fissure below the beak. The spines on the hinge-line 

 are also wanting, even if there exist indications that they have form- 

 erly been present, but that they have been worn away. There is 

 no doubt, however, but that our form belongs to the above-named 

 genus and species in question. 



Our specimen is larger than those of Waagen (from one-half 

 to once as large again), with a total length of 17 mm.; the width 

 at the hinge-line about 20 mm., and the thickness 11 mm. As con- 

 trasted with the specimens figured by Waagen, our specimen pre- 

 sents certain marks of senility; this being specially visible in Fig. 

 13, which gives a lateral view of the shell. Waagen distinguishes 

 two varieties of the species; the one strongly inflated, with small 

 wings, and the other less strongly inflated, with larger wings. Our 

 specimen belongs to the strongly inflated variety, and agrees fairly 

 closely in form with Waagen's Figs. 7 a — d. Our specimen, how- 

 ever, has had its greatest width at the hinge-line, which, unfortun- 

 ately, is somewhat defect, while Waagen's figure has its greatest 

 width at the middle of the shell. 



In the sculpture, our form presents certain small differences 

 from Waagen's description and figure. The radial sculpture with 

 ribs, the sinus and the nose-shaped projection at the anterior mar- 

 gin, are in entire agreement with the exception of some small lesions 

 suffered by the shell during the animal's life, but which had healed 

 again. A distinct difference, however, is that, in our specimen, the 

 umbonal portion of the ventral valve possesses concentric wrinkles 

 or rounded ribs, which are most evident pretty near to the umbo 

 and decrease in strength anteriorly. The valve presents scars of 

 spines in several places. 



We do not wish to express any opinion whether these differ- 

 ences: the concentric sculpture on the umbonal portion and the 

 richer occurrence of spines — are of such importance that they 

 entitle us to add a variety to Waagen's species, as the material 

 available consists of but one specimen, and as Waagen's description 

 suggests that there exists a certain space of variation in the case of 

 the Indian species. 



