FORMATIOIirS AISTD FOSSILS OF SOUTH MAFCHUBIA 61 



3909. Maclurea Mgsl)yi Geabau and Shimee, North Amer. Index Fossils, vol. 1, 



p. 664, fig. 919. 

 1930. Maclurea tofangoense Kobayashi, Jap. Journ. Geol. and Geogr., vol. 7, 



pts. 3, 4, p. 96, pi. 9, figs, la-c, 2, 3 ; pi. 10, fig. 2, pi. 11, fig. 7. 



This species occurs abundantly at several horizons wherever the 

 Middle Ordovician beds outcrop in Manchuria. Since a number of 

 nearly entire specimens are in hand, even though most are casts, 

 the major characters of the species are readily determined. 



Description. — Sinistral shell with flat spire, convex and widely 

 umblicated base, deep umbilicus, three or four whorls. The rapidly 

 enlarging whorls and other features seem to indicate that this species 

 is identical with Maclurites Mgshyi (Hall) from North America. 



The dimensions of the best Manchurian specimen are as follows: 

 The largest diameter of the upper surface is 50 mm ; the correspond- 

 ing width of the aperture, 18 mm; and height near the aperture, 

 18 mm. 



Formation and locality. — Middle Ordovician, Ssuyen formation: 

 Upper and lower fossil horizon of the black banded limestones near 

 Pen-hsi-hu, Niu-hsin-tai, and Tao-yuan-kou collieries, Liao-tung, 

 Manchuria. 



Pledotypes.—U.B.'^.M. Nos. 83671, 83672, and 83673. 



MACLURITES NITIDA (Ulrich and Scofleld) ? 



Plate 12, Figure 9 ; Plate 13, Figures 1-3 



1897. Maclurea nitida Ulbioh and Scofield, Geology of Minnesota, Paleontol- 

 ogy, vol. 3, pt. 2, p. 1040, pi. 75, fig. 11. 



1930. Maclurea niuhsintaiense Kobayashi, Jap. Journ. Geol. and Geogr., vol. 7, 

 nos. 3, 4, p. 97, pi. 10, figs. 5a— c. 



A well-preserved cast, a section of a shell, and one fragment con- 

 stitute the material on which this specific reference is based. 



As shown in Plate 13, Figures 1 and 2, the rather small shell, 

 comparatively narrow, deep, and rather abrupt umbilicus, rather 

 high and convex whorls, and other features cause me to think this 

 species quite similar to Macliorites nitida (Ulrich and Scofield) from 

 the Stones River, The Manchurian specimens may differ slightly 

 in having a comparatively round outer angle and a somewhat more 

 angular margin of umbilicus; nevertheless it seems to me that these 

 differences may originate from differences of preservation; viz, 

 the Manchurian specimens found up to the present time are casts 

 only, while the American specimens retain some parts of the shells. 



The Manchurian form is also related to Maclurea neritoides Eich- 

 wald from No-lu-ping, Tung-hu-hsien, Hu-pei, South China, but 

 is distinguished by its comparatively round outer angle, narrower, 

 abrupt umbilicus and the rather angular margin of umbilicus. 

 101621—32 5 



