104 AMERICAN JOURNAL 



Helictohrachiata, composed of an Athyris and two species of 

 Rhynchonella. This fell to the ground, and in 1855 he proposed 

 to apply the name to the group already characterized by King 

 as Epithyris. 



Under the impression that his early name was inadmissible, 

 Prof. King again described the group, with the same type, under 

 the name of Dielasma. 



According to the strictest rules of nomenclature Einthyris 

 must take the precedence, and Dielasma be considered as a 

 synonym. 



Subgenus Pygope, Link. 



Pygope^ Link, Physik. Erdbeschr. ii, 1830. King, Perm- 

 Foss. p. 144, 1850. Woodw., Man. Rec. and Foss. 

 Shells, p. 215, pi. XV, fig. 2. 



Antinomia, Catullo, Quart. Journ. Geol. Soc. vol. vii, 1850, 

 p. 74. 



Loop as in Terehratula. Shell punctate. Young bilobed, 

 the emargination being in the median line. In the adult the 

 inner edges of the valves unite, leaving a circular perforation in 

 the centre of the shell. 



Type. Pygope diphya^ = Terehratula dipJiya, v. Buch, Ueb. 

 Ter. p. 88, pi. 1, fig. 12. 



Fossil in Jurassic beds of Europe. 



The very remarkable conformation of the adult shell cannot 

 have been without some corresponding differences in the soft 

 parts, and is sufficient to entitle the group to subgeneric rank, 

 although the apophyses resemble Terehratula. 



Another species, P. diphyoides^ d'Orb. (Pal. Fran. Ter. Cret. 

 iv, p. 87, pi. 109), is found in the Neocomian of France. 



The recent species of the genus Terehratula, not previously 

 mentioned, are : 



Terehratula uva, Brod., P. Z. S. 1833, p. 124. Ilab., Gulf of 

 Tehuantepec, Cuming ; Falkland Ids., Davidson. 



? Terehratula minor, Phil, and Suess., Dav. Ann. Nat. Hist. 

 1861, p. 35. Ilab., Mediterranean. 



Terehratula Davidsoni, A. Adams, P, Z. S. 1867, p. 314, pi. 

 19, fig. 30, Satanomosaki, Japan, 55 fathoms. 



?? Terehratula transversa, Gould, Proc. Bost. Soc. Nat. Hist, 

 vol. vii, p. 323, Sept., 1860. Otia Conch., p. 120. Dav., Ann. 

 Nat. Hist. 1861, p. 38. (Not T. transversa, Sby., which is a 

 synonym of T. dorsata, Lam.) Suess. Wohns. i, p. 27, 1859. 



