SPONDYLUS. 129 
1885. SponpyLtus xQuatis, Lundgren. Spondylusart. i Sverig. Kritsyst. (Sverig 
Geol. Undersoék., ser. C, No. 69), p. 5, 
pl. i, figs. 1—3. 
1889. — — O. Griepenkerl. Senon von Kénigslutter (Paleont. 
Abhandl., vol. iv), p. 38. 
— — spinosus, . Holzapfel. Die Mollusk. Aachen. Kreide (Paleon- 
tographica, vol. xxxv), p. 248, pl. 
xxvii, figs. 12, 13. 
— — — A, Fritsch. Stud. im Gebiete der béhm. Kreide- 
format. IV. Die Teplitzer Schicht, 
p- 85, fig. 81. 
1897. = — H. Woods. Quart. Journ. Geol. Soe., vol. liii, p. 385. 
— — —- R. Leonhard. Kreideformat. in Oberschles. (Paleon- 
tographica, vol. xliv), p. 50. 
- — mQquauis, A. Hennig. Revis. Lamell. i Nilsson’s ‘ Petrif. 
Suecana’ (Kon. Fysiogr. Sillsk. 1 
Lund. Handl.,N. F., vol. viii), p. 25. 
1898. — sprnosus, G. Muller. Mollusk. Untersen. von Braunschweig u. 
Ilsede (Abhandl. d. k. preuss. geol. 
Land.,n. F., pt. 25), p. 23, pl. iv, fig. 4. 
Description.—Shell regular, ovate, slightly imequilateral, rounded ventrally, 
more or less pointed and produced in the umbonal region, where the margins are 
only slightly curved. Valves sometimes equally convex, but the right usually 
flattened ; convexity greatest in the median line, towards the umbo. 
Right valve a little larger than the left, with the dorsal part of the posterior 
border longer than the corresponding part of the anterior border. Ribs stronger 
than those of the left valve, separated by deep narrow grooves; the grooves are 
crossed by rather irregular linear ridges. In some specimens almost every rib is 
divided into two parts by a narrow median furrow—the furrows starting, in 
different specimens, at varying distances from the umbo; in others only a few ribs 
(often near the centre of the valve or near the anterior and posterior borders) are 
so divided; or all the ribs may be undivided. Long shghtly curving spines, with a 
groove on their upper surfaces, are borne at intervals by some of the ribs— 
frequently by eight, and grow out radially, those near the margin of the valve 
extending outwards in all directions roughly parallel to the plane of the valves; 
the spines near the anterior and posterior margins are the strongest. The ribs 
bearing spines are often not divided by a groove. 
Left valve with from 26 to 51 regular, rounded ribs, occasionally bearing short 
spines ; the grooves between the ribs may be wider or narrower than the ribs, and 
are crossed by many rather irregular linear ridges, which sometimes extend on to 
the ribs. The ribs may be (1) all of uniform size, separated by broader grooves, 
and are then relatively few in number and stout; or (2) the stronger ribs may 
alternate regularly with smaller ribs introduced in the grooves at varying distances 
ilr¢ 
