Vol. I. M. S. Chang : — Brachiopoda from the Orthis Bed (iii) 15 



of the Neichia Formation 



is surrounded on both sides by a deep depression into M-hich short spines are 

 pointing from the edge of the mold. In two other specimens a slight sinus is also 

 shown. The surface is covered by about thirty rounded plications with wider 

 interspaces and numerous intercalations, especially in the central part of the shell. 

 Measurements: 



Greatest width = 13 mm 



Hinge line = 12.5 mm 



Height =11 mm 



Proportion of height to width = 1.18 



Remarks: This species is made a new variety because it differs from Orthis 

 calligramma in having intercalations in its plications. The plications of Orthis 

 calligramma always remain simple. 



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

 Nos. X 224, X 225, X 227; Cat. Nos. 3377, 3378, 3379). 



9. Orthis cf. unguis Sowerby 



PI. II, fig. 5a-d. 



cf. 1869. Orthis unguis Sow. Davidson, British Fossil Brachiopoda, Pt. VII, No. Ill, p. 257, pi. 

 XXXVII, figs. 16-22. 



Two specimens representing the interior mold and the exterior impression 

 of the pedicle valve are known. They are very imperfect and a discriminate de- 

 termination is impossible. They are referred to Orthis cf. unguis Sow. because 

 their plications are very angular, a fact not known in the case of Orthis calligramma. 



The shell is rather small, having a length of four mm. and a width of about 

 six mm. It is almost fiat and is ornamented by about fourteen simple and angular 

 plications which when viewed from the front simulate the cross section of a roof. 



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

 Nos. X210, X211; Cat. Nos. 3381, 3382). 



10. Orthis cf. calligramma Daiman, var. subplicata Reed. 



PI. II, Fig. 6a-d. 

 cf. 1917. Orthis calligramma Daiman, var. subplicata Reed. The Ordovician and Silurian Brachiopoda 

 of the Girvan District, p. 828. pi. V, figs. 10-15. 



Only interior molds of the pedicle valve of this sj)ecies are known. The speci- 

 mens are rather imperfect and an exact identification is, therefore, difficult. 



