Vol.1. M.S.Chang: — Brachiopoda from the Orthis Bed (in) 13 



of the Neichia Formation 



tion and branching of the plications, thus increasing the number to nearly forty, 

 and (3) seven plications in the sinus instead of four, with arrangement as shown in 

 Text-Figure 3. 



Text-Fig 3. Arrangement of the sinal plications in specimen No. X 220. 



An internal mold of the pedicle valve is shown by No. X 215, PI. I, Fig. 10a. 

 It is convex, with the beak region slightly incurved. The fold is not prominent. 

 The surface ornamentation consists of more than forty plications which show more 

 bifurcations and intercalations along the fold than in any other place. 



An imi)ression of the exterior of the pedicle valve (No. X 219 PI. I, Fig. 11a) 

 is a little larger and has a slight fold (representing the sinus). Its plications are 

 much more numerous because of their profuse intercalations and bifurcations. 



Remarks. This species is characterized by a distinct though ill-defined fold 

 in the pedicle valve and a well-developed sinus in the brachial valve. It resembles 

 Orthis calligramma only in having strias in the interspaces of the plications. In the 

 order described the plications increase in number and grow more complicated. 

 Whether this represents a state of progressive evolution is difficult to say, because 

 the specimens at hand are too few to offer a definite explanation. 



Horizon and Locality: Occurs with the preceding. Coll. C. C. Yii. (Ser. 

 Nos. X 215, X 216, X 218, X 219, X 220; Cat. Nos. 3373, 3371, 3370, 3374, 3372). 



7. Orthis ellipsoides ciaang (sp. nov.) 



PI. I, Fig. i2a-d. 



Specimens Nos. X 209 (PL I, Figs. 12b, 12a) and X 201 (PL I, Figs. 12c, 12d) 

 represent the interior mold and the exterior impression of the pedicle valve respec- 

 tively, which, when put together, fit into each other exactly. The species is of 

 subelliptical outline, much wider than high. The hinge fine is not well preserved, 

 the shoulders sloping gently from the beak to the cardinal extremities which ap- 

 parently mark the greatest width. The interior mold shows the rostral cone separat- 



