182 Art. 6.— M. Yokoyama : 



This species is fully described in the above cited work of 

 Davidson. In general the shell is ovate in form, longer than wide, 

 with valves almost equally convex. The surface-sculpture consists 

 of very fine radiating striae which in our water-worn specimens 

 are hardly distinguishable except with a lens. 



The specimens are very fréquentât Koshiba being found in 

 hundreds, but are mostly more or less distorted, so that it is very 

 difficult to obtain a perfect and undistorted specimen. Neverthe- 

 less, we can discern a great variation occurring in their outline. 

 According to the measurements given by Davidson, the propor- 

 tions of length to breadth are 10 to 8. Among our fossils a more 

 elongated shape predominates, so that the length is to the breadth 

 as 10 to about 7,3. But there are specimens which are more like 

 those figured by Davidson. The thickness of the shell is some- 

 w r hat less than one-half the length. 



In general the fossil forms seem to be somewhat smaller than 

 the living, for none of them exceed 40 millim. in length, while 

 Davidson figures one of 50 millim. 



Fossil occurrence. — Kanazawa Zone (Kanazawa); Koshiba 

 Zone (Koshiba); Naganuma Zone (Naganuma). 



Living. — Central and Western Japan. Davidson states that 

 the species lives between 100 and 250 fathoms. 



234. Terebratulina caput-serpentis, (Linné). 

 Pl. XIX. Figs. 15, 16, 17, IS. 



Terebratulina caput-serpentis. Davidson, Monogr. Eec. Brach., p. 17, pl. Ill, ffg. 12, pl. IV. 

 figs. 1-11, pl. V, figs. 32-34. Seguenza, Pal. Malac. dei Ter. Terz, del Dist. di Messina, p. 44. 

 Wood, Crag Moll., Bivalves, p. 169, pl. XI, fig. 3. Nyst, Conch. Terz. Tert, de la Belgique, p. 

 250, pl. XXVIII, fig. 3. Brauns, Geol. En v. Tokio, p. 74. 



Anomia caput-serpentis. Linné, Syst. Nat. ed. 12, vol. I. p. 1153. 



This is the species which I formerly took lor Terebrutid'ma 

 cailleti Crosse (Jour. Geol. Soc. Tokyo, vol. XVII, no 201, p. 2) 

 but which as I am now convinced, is nothing else than the cos- 

 moplitan species of Terebratulina, T. caput-serpentis L. Our speci- 

 mens agree most with the so-called variety méditer ranea. Of about 

 six specimens which we possess, the perfect and undistorted ones 



