94 DE. T. DAVIDSON ON EECENT BRACHIOPODA. 



however, iu being subtetiagonal and tapering more anteriorly, with a less sharply defined 

 mesial depression or sinus in the dorsal valve, and by its ribs being more angular, 

 and more especially by its elevated mesial Magasella-sha])ed septum, which is always 

 observable in the interior of the dorsal valve in its adult condition, while, on the contrary, 

 in fully-developed examples of Terebt^atella dorsata of similar dimensions the septum 

 rises but little above the bottom of the valve. The mode of attachment of the loop of 

 the septum is also different in detail. 



In 1845, Philippi described, in the ' Archiv fiir Naturgeschichte,' a Terehratula under 

 the name of T. rlwmbea, a shell similar in shape and character to Magasella jlexuosa. 

 The type is in the Royal Zoological Museum of Berlin. Philippi did not figure his 

 shell, and I am indebted to the kindness of Prof. E. von Martens for the figures I am 

 able to give of the so-termed species, which I believe to be a full-grown example of 

 Terehratula Jlexuosa, P. King (PL XVII. figs. 6-8 a). It is also stated to have been 

 procured from the Straits of Magellan. 



Terebratellu Jlexuosa is the type of Ball's subgenus Magasella. He states that " the 

 punctures [on the surface of the shell] are very large, circular, and under the glass 

 recall the cells of Polyzoa. The margin of the valves is sharply crenulated from the 

 extremities of the external plications." 



Magasella Jtex'uosa does not seem to attain to the dimensions of Terehratella dorsata. 



Under the name Terehratella suffusa,, L. Reeve describes (Monogr. Terehratula, pi. v. 

 fig. 18) what he admits to be a doubtful sj)ecies partaking of the general character of 

 Terehratula dorsata. In 1861 Mr. Reeve kindly presented me with his type and the only 

 specimen of the so-termed species with which he was acquainted. The specimen measures 

 9 lines in length by 8 in breadth and 5 in depth, and is not symmetrical, one half 

 being narrower than the other, or, in other words, it is to some extent a malformation. 

 Mr. Reeve says that it shows no indication whatever of a mesial depression in the 

 dorsal valve ; but this is a mistake, for in reality there exists a slight depression. In 

 the interior of the dorsal valve there is a large prominent mesial septum to which the 

 principal branches of the loop are attached previously to being reflected, exactly as we 

 find to be the case in Magasella Jl£xuosa, to which species therefore I would refer 

 Reeve's species (PI. XVII. figs. 14 a, h, 15), No specimen of this size of Terehratella 

 dorsata presented a similarly shaped and elevated septum. Terehratula snjfusa is 

 evidently a malformation, and its habitat is not known, but it was in all probability 

 obtained in the Straits of Magellan. 



50. Magasella crenulata, Sowerby, sp. (Plate XVII. figs. 9-11.) 



Terehratula crenulata^ G. B. Sowerby, Descriptions of 13 new Species of Brachiopoda, Proc. Zool. Soc. 

 1846, p. 91 ; and Tlies. Concli. vol. i. p. 358, pi. 71. figs. 96-98, 1846. 



Tercbratella crenulata, Davidson, Ann. & Mag. Nat. Hist. 2nd ser. vol. ix. p. 368, 1852; E. Suess, 

 Ueber die Wohnsitze der Brachiopoden, Sitzungsb. k. Akad. Wissenscli. Wien, p. 206, 1859. 



Magasella crenulata, Woodward & Gray, A Catalogue of tbe Brachiopoda in the British Museum, 

 p. 98, 1853. 



Terehratula {Magas) crenulata, L. Reeve, Conch. Icon. Mon. Terehratula, pi. viii. fig. 32, 1861 ; and 

 Ann. & Mag. Nat. Hist. 3rd ser. vol. vii. p. 179, 1861. 



