38 JURASSIC BIVALVIA AND GASTROPODA 



Modiolus virgulinus (Thurmann & Etallon) 

 PI. 3, fig- 8 



1862. Mytilus virgulinus Thurmann & Etallon : 224, pi. 29, fig. 6. 

 1875. Mytilus virgulinus Etallon ; de Loriol : 152, pi. 18, figs. 17, 18. 

 i960. Modiolus virgulinus (Etallon) ; Joubert, pi. 6, figs. 12a, b. 



Material. One specimen (no. L.92181). 



Locality and horizon. 3 miles N.E. of Melka Dakacha, N.E. Kenya ; Upper 

 Kimmeridgian, Dakacha Limestones. 



Remarks. This specimen agrees very closely in shape with de Loriol's fig. 18, 

 cited above. It is, however, rather eroded near the dorsal margin and so does not 

 show the strong growth-rugae which are confined to this region in typical specimens 

 of the species. M. virgulinus, as its name suggests, occurs in France in the " Virgu- 

 lian " stage of the Kimmeridgian. 



Subgenus INOPERNA Conrad 1875 



Modiolus (Inoperna) sowerbianus (d'Orbigny) 

 PI. 3, figs. 10, 11 



1819a. Modiola plicata J. Sowerby : 87, pi. 248, fig. 1 (non Mytilus plicatus Gmelin 1791). 



1850a. Mitylus [sic] sowerbianus d'Orbigny : 282. 



1910. Modiola plicata Sow. ; Dacque : 30, pi. 5, fig. 10. 



1940. Modiolus (Inoperna) plicatus J. Sowerby ; Cox : 71, pi. 5, figs. 13, 14. 



Material. Two fragments from the Toarcian ; several specimens from higher 

 beds. 



Localities and horizons. Didimtu hill, 2 miles S. of Bur Mayo, N.E. Kenya ; 

 Upper Lias, Toarcian, Didimtu Beds. Korkai Hammassa, 19 miles E. of Takabba, 

 N.E. Kenya, and Tifo, 14 miles N. of Wergudud, N.E. Kenya ; Oxfordian, Golberobe 

 Beds. 



Remarks. In this species each of the strong oblique ribs which meet the dorsal 

 margin of the shell splits up half-way to the diagonal carina into from three to 

 several weak ribs, or is replaced by them without distinctly splitting up. This 

 feature of the ribbing is observable in the Toarcian specimens now recorded and in 

 the best preserved one from higher beds. 



D'Orbigny's replacement name is here adopted for the species in consequence of 

 the Article 59(b) of the International Code, whereby secondary homonymy pro- 

 duced prior to 1961 (in this case by d'Orbigny's transference of Sowerby's species to 

 Mytilus) requires a permanent change of the specific name. 



