BRACHIOPODA. 61 



there is no doubt tliat the conspicuous latei'als correspond more or less exactly 

 with the laterals, and the central scar with the centrals in Lingula. Lingulepis 

 also bears a broad and low median ridge, elevated along its margins and de- 

 pressed in the middle, similar to, but fainter than that in L. anatina. Although 

 the similarity to Lingula in these respects is evident, a much closer homology 

 is found in the muscular scars of this valve of Lingulepis and that of Lingulella. 

 This is seen in the crescentic laterals and the prominent central in Lingulella. 

 \n Obolella, the posterior coalescence of these scars is even more prominently 

 developed than in Lingulella. 



In the muscular scars of the brachial valve, the divergence from Lingula is 

 still more marked. These impressions make a conspicuous tlabelliform scar, 

 extending medially about one-half the length of the shell. The central portion 

 of this scar is accompanied on either side by broader, partially resolvable lateral 

 scars, all the subdivisions of the impression coalescing in the umbonal region. 

 Here the crescentic laterals of Lingulella and Obolella are quite absent, but the 

 posterior coalescence of all the scars into one broad and ill defined impression, 

 is a feature noticeable in all of these genera. Thus the genus Lingulepis affords 

 an important connecting link between Lin.gula and Lingulella in the direct line 

 of relationship to Obolella and its allied genera. 



The shell-structure of Lingulepis is, presumably, closely similar to that of 

 Lingula, and, as usually in that genus, its surface-ornamentation is uniformly 

 of concentric lines. L. ■pinniformis also shows a few faint radiating lines, which 

 are more .strongly developed on the internal surface over the anterior portion 

 and on the interstitial lamellae of the shell. 



The genus, as far as known, is represented only in American primordial 

 faunas ; L. pinniformis, of the Potsdam sandstone of Minnesota and Wisconsin, 

 finds a closely allied species in L. antiqua, Hall, of the same formation in New 

 York. Two species, L. cune.olus and L. perattenuata, have been described from 

 the Black Hills, by R. P. Whitfield,* and in the same year Hall and Whit-. 

 FiELDf referred three species to this genus, L. Ella, L. Mara and L. ? minuta. 

 The first of these has since proved a Lingulella, and it is probable that the 



* Preliminary Rept. Geology of the Black Hills. 1877. 



t King's Report United States Geolog-ical Exploration Fortieth Parallel. 



