368 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. 57. 



It was not at first understood that certain species stopped short 

 in their development at particular stages while others reaching that 

 stage continued their evolution. In fact the confusion, or perhaps 

 it would be better to say the doubtful points, are not yet entirely 

 cleared up. 



Our series of Terehratella dorsata is quite small and perhaps should 

 not form the basis of any dogmatic opinion, but from the material 

 which has passed through my hands I feel confident that T. flexuosa 

 King is distinct, adult, and not a stage of T. dorsata, as it has been 

 sometimes regarded. In this opinion I am supported by the views 

 of Davidson and Ihering. 



On the other hand T. evansi and T, valenciennesi, of which I have 

 never seen authentic specimens, are admitted by Davidson and the 

 majority of writers to be developmental stages of T. dorsata or some 

 other similar species. 



StiU another form, which by some authors is regarded as a muta- 

 tion of T. dorsata, seems distinct, as I have already indicated under 

 the head of T. soweriii King. 



In 1891.* I indicated the probable relations of the various small 

 species of Magasella then known, and not much can be added even 

 now, to that statement. The few species of doubtful relations will 

 here be considered separately. 



MAGASELLA FLEXUOSA King. 



Terebratula flexuosa King, Zool. Journal, vol. 6, p. 337, 1831. — Sowerby, Thes. 

 Conch., vol. 1, p. 347, pi. 69, figs. 23-24, 1847.— Davidson, Ann. Mag. Nat. 

 Hist., ser, 2, vol. 9, p. 367, 1852. 



Magasella flexuosa Dall, Amer. Joiu"n. Conch., vol. 6, p. 135, 1870; Proc. Acad. 

 Nat. Sci. Phila. for 1873, p. 189. 



Magasella evansi Dall, Amer. Journ. Conch., vol. 6, p. 134, 1870, not of Davidson, 

 1852. 



Terebratula rhomhea Philippi, Arch. f. Naturg., vol. 11, pt. 1, p. 59, 1845; (accord- 

 ing to Davidson) Mon. Ilec. Brach., pi. 17, figs. 6-8 a, 1887. 



Magasella flexuosa Davidson, Challenger Brach., p. 46, pi. 4, fig. 5, 1880; Mon. 

 Rec. Brach., pt. 2, p. 92, pi. 17, figs. 1-5, 1887. 



Type locality. — Port Famine, Magellan Strait. Captain King. 



Cat. No. 



Locality. 



Collector. 



Number 

 of speci- 

 mens. 



11783 



17822 



96221 



332787 



Orange Harbor, Patagonia.. 

 Orange Harbor, Patagonia. 

 Magellan Strait, 61 fathoms 

 Magellan Strait , 



U. S, Exp. Ex 

 U. S. Exp. Ex 



B. F 



Fulton 



I have expressed under the heading of the genus my opinion as 

 to the distinctness of this species, which appears to me to have 



» Proc. Acad. Nat. Sci. Phila. for 1891, p. 170. 



