N0RTIIUMI5EIlLAIsD AND DURHAM. 249 



amis were most probably attached. Tlic muscular impressions 

 on this valve have each a triangular form, and as they are placed 

 close to each side of the median plate, they have together a fan- 

 shaped appearance. They are considerably raised, and most so on 

 the anterior margin. Their surface is sciilptured out into deep 

 curved linear hollows for the attachment of the muscles. The 

 surface round about these muscles and the cardinal regions is 

 neatly pitted, causing small pimples on the casts; these are pro- 

 bably the ovarian spaces, and the pittings indicate, according to 

 Mr. A. Hancock's very valuable researches on tlie Anatomy of 

 the recent Brachiopoda, the points of attachment of small mus- 

 cles spread over the inner surface of the ovaries to fasten the 

 latter to the shell. One observes similar markings on the cor- 

 responding parts of the other valve. 



It is generally supposed that the reniform callosities are con- 

 nected with the vascular system, but this supposition appears to 

 be false, and is unsupported by a comparison of these processes 

 with the corresponding parts of other Brachiopods. If we com- 

 j)are them, for example, with the same valve of Argiope^ or of 

 Thecidiwn, genera which show points of resemblance to this in 

 several particulars, we find that similar processes have served for 

 the attachment of the oral arms ; and this view is supported by 

 all that we know^ of the position of these arms in both recent 

 and fossil genera. At least, these structures cannot be attri- 

 buted to the vascular system, or they would undoubtedly be pre- 

 sent in both valves, whereas they are confined to one. 



On some casts of this Productus a great number of small 

 parallel grooves or furrows are seen running from the central 

 ovarian region to the anterior margins of the valves; they are 

 not very distinct, but they may, perhaps, hereafter be found to 

 have been connected with the vascular system. This idea is 

 somewhat strengthened by the a]3pearance of similar lines on 

 some casts of Spirifer^ which few persons Avould hesitate to pro- 

 nounce as vascular sinuses. There remain to be noticed on this 

 small valve the curious spine-like callosities which stud the 

 whole of the anterior portion of the shell ; they are strongest 

 where the produced, curved -u]) portion of the margin takes its 



