BRACHIOPODA. \ 89 



In the brachial valve, the posterior portion of the margin is considerably 

 more flattened and that portion of the outline of tlie valve quite transverse. 

 Directly within this margin, and parallel to it, is a narrow tliickened hand, 

 which may be analogous to the callosity occupying a similar position in 

 Waagen's genus Neobolus. There is also a muscular thickening or callosity 

 of about the same size and character as that seen in the pedicle-valve, but 

 somewhat more flabellate, less distinctly defined, and not satisfactorily resolvable 

 into separate scjirs. A faint median septum begins near the posterior margin 

 of this area and grows in size nntil the anterior end is reached, whence it 

 rapidly disappears. No evidence has been found of curved laterals similar to 

 those in the pedicle-valve. Mr. Ulrich's figures show in both valves peculiar 

 circular scars situated near the lateral margins. These are mentioned in the 

 diagnosis as being "very faint" and indeed are visible only on the best pre- 

 served specimens, and there only under the most favorable illumination. If it 

 can be demonstrated that these markings actually represent muscular scars and 

 are not the result of a slight exfoliation, they will prove a feature of much im- 

 portance. None of the forms of Obolella, or allied genera known in primordial 

 or Silurian faunas, show a combination of the elongate curved lateral scars with 

 such additional impressions, and we find an analogous occurrence only in the 

 genus Lakhmina, ffihlert, from the Salt Range of India,* a genus with a well- 

 developed platform, remarkable not only as being the earliest representative of 

 the Trimerellids, but also for its synthetic characters, for in association with 

 the " laterals," or outside marginal scars, which undoubtedly represent the 

 terminal impressions of the crescent, are the peculiar curved laterals of 

 Obolella. Better material must be examined in order to determine the ex- 

 istence or non-existence of these crescent scars in Schizobolus. This genus, 

 with our present knowledge, appears to be a very late representative of the 

 true obolelloid type, as pointed out by Mr. Ulrich, varying therefrom more 

 in the character of its pedicle-slit and cardinal area than in any other 

 feature, but in its triangular pedicle-opening indicating a relationship to 

 Trematis and Schizocrania. 



* See Waagen, Mem. Geol. Survey of India, Sail Range Fossils, vol. i, pt. iv, fasc. 5, p. 764, pi. Ixxxv, 

 fig. 6, 1885 ; Davidxonella linguJoides. 



