32 JURASSIC BIVALVIA AND GASTROPODA 



Material. The holotype (no. L. 54109), described previously, and several para- 

 types and later collected specimens. 



Localities and horizons. S. of Tarawanda, 11 miles S.E. of Lugoba, Tangan- 

 yika ; Callovian. Scarp face, eastern margin of Makoko plain, Bagamoyo hinterland, 

 Tanganyika ; Oxfordian. Wilderri hill, n miles S.S.W. of Rahmu, N.E. Kenya ; 

 Upper Oxfordian, Seir Limestones. 



Remarks. The largest specimens are 90 mm. long. Among representatives of 

 Indogrammatodon this species is exceeded in size only by G. (I.) iddurghurensis Cox, 

 from the Argovian of India. The number of main ribs on the left valve may be as 

 few as 11, but is usually about 15. 



Grammatodon (Indogrammatodon) irritans (Hennig) 



PI. 2, fig. 3 



19146. Cucullaea irritans Hennig : 175, pi. 14, fig. 6. 



1933. Cucullaea irritans Hennig ; Dietrich : 26, pi. 2, figs. 23-32. 



i960. Grammatodon {Indogrammatodon) irritans (Hennig) ; Joubert, pi. 6, fig. 7. 



Material. Numerous specimens. 



Localities and horizons. Tendaguru neighbourhood (1 mile N. W. of Tendaguru 

 hill, Kindope, and Kipande path), Tanganyika ; Upper Kimmeridgian, Nerinella 

 and " Trigonia smeei " Beds. Kinjele, 5 miles W. of Mtapaia, N. of Tendaguru, 

 Tanganyika ; Upper Kimmeridgian, Indogrammatodon Bed. Dusse, i| miles S.E. 

 of Rahmu, N.E. Kenya ; Upper Oxfordian, Seir Limestones. Hereri river crossing, 

 3 miles S. of Melka Kunha, N.E. Kenya ; Kimmeridgian, Hereri Shales. 



Remarks. Compared with G. (I.) virgatus, this species is smaller, less elongate, 

 more strongly inflated, and more sharply carinate posteriorly, with a more pronounced- 

 ly concave posterior area. The largest specimens examined are about 35 mm. long. 

 The number of ribs anterior to the carina on the left valve is usually about 15, but 

 there may be one or two fewer. In some specimens the number on the right valve 

 is about the same, but in others it is considerably greater. In some right valves the 

 ribbing is only feebly developed near the posterior carina. 



Grammatodon (Indogrammatodon) matapwaensis sp. nov. 



PI. 2, figs. 6a, b 



Diagnosis. Small (length of larger specimen 17 mm.), rectangularly ovate, sub- 

 equilateral, not much elongated, well inflated, most so anteriorly to mid-length. 

 Umbo almost median, projecting to a moderate extent above hinge-margin. Poster- 

 ior area feebly concave, the boundary between it and the flank rounded off, not form- 

 ing a distinct carina. Flank and area ornamented with well separated, unevenly 

 spaced radial threads, with densely and regularly arranged concentric threads over- 

 riding them and occupying their intervals ; the radial threads are slightly the more 

 closely arranged on the right valve, where one or (rarely) two weaker intercalary 



