58 JURASSIC BIVALVIA AND GASTROPODA 



creek, Tendaguru, Tanganyika ; Upper Kimmeridgian, " Trigonia smeei " Bed. 

 Mpilepile stream bed, near Mitole, and Kiwawa stream, both northern Mandawa 

 area, Tanganyika ; Upper Kimmeridgian. 



Remarks. This species appears to be closely related to Chlamys (Radulopecten) 

 inacquicostata, recorded above, but is much smaller and has more ribs. The speci- 

 mens, although from four different localities, are all of about the same size, so that 

 it has been assumed that they are full-grown. 



Subgenus SPONDYLOPECTEN Roeder 1882 



Chlamys (Spondylopecten ?) badiensis Cox 



PL 7, figs. 3, 4 

 1952. Chlamys [Spondylopecten ?) badiensis Cox : 16, pi. 1, figs. 14a, b. 



Material. Two specimens (nos. L. 93552, LL. 35099), the latter ex B.P. Coll. 



Localities and horizon. Namakambe stream, Mandawa-Mahokondo anticline, 

 Tanganyika ; probably Callovian. \ mile N.W. of bridge over Mkulumuzi river, 

 2 miles W. of Tanga, Tanganyika ; Callovian. 



Description. Both specimens have 23 rounded, moderately prominent ribs, as 

 in the holotype of C. badiensis. In one specimen the dorsal margins of the body of 

 the shell are concave and extend almost to the middle of the height of the valve, 

 the ventral margin of which forms a semicircle. In the second specimen the dorsal 

 margins are relatively short, extending only to the dorsal third of the height of the 

 valve, and the ventral margin is semi-elliptical. Although the two specimens thus 

 differ considerably in outline, it is thought that they belong to the same species. In 

 the first and less eroded specimen, a right valve 28 mm. high, the ribs bear a median 

 and two lateral rows of small scales, together with regular, delicate transverse 

 striations which are arched towards the umbo. The narrow, V-shaped intervals 

 are also transversely striated and are bordered on each side by a longitudinal thread 

 at the base of the adjacent rib. The second specimen, a left valve of about the same 

 height, retains traces of similar ornament in places. The auricles are imperfect in 

 both specimens, but can be seen to bear squamose or beaded radial riblets. 



Remarks. C. badiensis, the holotype of which came from the Callovian of Cutch, 

 is closely related to the French Callovian species C. palinurus (d'Orbigny) (see 

 Cossmann, 1913a : 2, pi. 11, figs. 1-4 ; 1924 : 29, pi. 5, figs. 5, 6), but in that species 

 the number of ribs is only 20. Other related forms are C. syriaca Cossmann (1925 : 

 325, pi. 8, figs, ya-c), with about 30 ribs, and C. macfadyeni Cox (1935a : 176, pi. 18, 

 figs. 11a, b), with 19 ribs. All possibly could be geographical races of C. palinurus. 

 The ligamental area of the right valve has not been observed in any of these forms, 

 but their tentative reference to Spondylopecten is suggested by their external simi- 

 larity to Pecten erinaceus Buvignier, its type species. 



