OF CONCHOLOGY. 166 



needs revision. Assuming the relative identity of the valves, as 

 Prof. Hall has indicated, the impressions are as follows : 



In the neural valve the scars of the adjuster muscles are situ- 

 ated on each side between the outer edge of the visceral area 

 and the extreme edge of the hinge line near its outer end. The 

 visceral area is traversed by a broad mesial ridge projecting a 

 little beyond the edge of the area and abruptly truncate. At 

 the outer angles of this end of the ridge are the ovate (and some- 

 what anteriorly divaricate) scars of the anterior adjusters, before 

 which is a broad space, probably the seat of the anterior re- 

 tractors. The visceral area is anteriorly prolonged into two 

 narrow arms which pass between the lateral and median scars 

 and nearly encircle the latter. (See pi. 6, fig. 5, 6.) 



In the other valve the lateral scars are not visible ; the an- 

 terior adductors ;jeem from the figure to divarcate posteriorly, 

 being very narrow and divided in the middle by a pointed lobe 

 of the visceral area, and bounded on the outer sides by two broad 

 pointed lobes of the same. 



The position of the apex removes the shell from Spondylohus, 

 The groove or emarg?nation of the hinge line of both valves, as 

 well as the form and position of the muscular scars, would also 

 seem to prevent it from being placed in Oholella. It would 

 seem to belong to an undescribed genus, but, in the absence of 

 specimens, I do not feel warranted in characterizing it from 

 figures alone, especially as the figures of Obolella, given by Mr. 

 Billings, are very poor. 



Since the first part of this paper was in type I have been in- 

 debted for facilities for study and other favors to Prof. Agassiz, 

 of the Museum of Comparative Zoology, at Cambridge ; Mr. 

 Hyatt, of the Boston Society of Natural History ; Prof. James 

 Hall, State Geologist, of New York, Mr. J. G. Anthony ; Mr. 

 R. P. AVhitfield, of Albany; Mr. Geo. W. Tryon, Jr., of 

 the Philadelphia Academy of Natural Sciences, and especially 

 to Mr. E. S. Morse, of Salem. To the last named gentleman I 

 am indebted for the privilege of examining his beautiful ana- 

 tomical drawings of various brachiopods, some of them taken 

 from life, and for specimens of Grlottidia ■py7'amidata. Among 

 Mr. Morse's drawings were some of a singular Sipunculoid worm, 

 which would appear, from them, to have an anterior termination 

 to the intestine, thus forming a notable exception to the general 

 rule among worms. While dissenting entirely from the conclu- 

 sions at which he has arrived, from his study of the brachiopods, 

 I must express my full appreciation of his kindness in thus open- 

 ing his portfolio for my examination, and of the value of his re- 

 searches into the embryology and anatomy of this interesting 



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