BRACHIOPODA. 81 



impressions in Oboli^lla which have been designated by this term, but more 

 nearly to that of the terminal scars oF the crescent in Dinobolcs. The median 

 area of the valve on each side of the septum is much thickened, and at its 

 anterior edge lie the conspicuous central scars. hi the brachial valve the 

 cardinal and "lateral" (external or terminal) impressions are developed as in 

 the opposite valve, and in the central region is a pair of curved impressions 

 suggestive of, and probably corresponding to the elongate laterals in Obolklla. 

 These enclose an indistinct central scar. 



The affinities of Obolus with the linguloids are somewhat remote and sicneral, 

 but are seen in the character of the cardinal area and the disposition of the 

 central muscular scars in the pedicle-valve. The strongly thickened median 

 area of the same valve, which is given prominence by the excavated central 

 scars, is suggestive of a rudimentary platform such as is found with greater 

 development in Lingulops, Lingulasma and the Trimerellids. This, however, 

 may be an homology only, as the nmscular scars in Obolus are not situated 

 upon, but at the anterior margin of this area. The external muscular impres- 

 sions with the ridge proceeding from them backward, toward the umbo, suggest 

 the crescent in Dinobolus, and are the equivalents of the terminal crescent 

 scars in that genus and the externals in Obolella, while the curved laterals in 

 the brachial valve show, as just noticed, the near relationship to the latter 

 genus. 



A species from the St. John group, at Caton's Island, King's county. New 

 Brunswick, has been referred to this genus by Mr. G. F. Matthew,* Ijut we 

 have, as yet, no knowledge of its interior characters, and the reference requires 

 verification. The exterior of both valves of this shell is ornamented in the 

 umbonal regions by a reticulated punctation which is apparently superficial. 

 This becomes obsolete with tlie later growth of tli" <hell. (See Plate IV k, 

 fig- 22.) 



* 0. pulckei; Matthew. Canadian Record of Science. .T.uin nv lsS9, ]). 306. 



