SPONDYLUS. 129 



1885. Spondylus ^qualis, Limclgren. Spondylusart. i Sverig. Kritsyst. (Sverig 



Geol. Uudersok., ser. C, No. 69), p. 5, 

 pi. i, figs. 1 — 3. 



1889. — — 0. GviepenJcerl. Senon von Konigslutter (Palaeont. 



Abhandl., vol. iv), p. 38. 



— — spiNOsus, E. Holzapfel. Die Mollusk. Aachen. Kreide (PaliBou- 



tographica, vol. xxxv), p. 243, pi. 

 xxvii, figs. 12, 13. 



— — — ^- Fritsch. Stud, ini Gebiete der bohm. Krcide- 



format. IV. Die Teplitzer Scliicht, 

 p. 85, fig. 81. 



1897. — — H. Woods. Quart. Journ. Geol. Soc, vol. liii, p. 385. 



— — — -B. Leonhard. Kreideforniat. iu Oberschles. (Palaeon- 



tographica, a'oI. xliv), p. 60. 

 - — j.QUALis, A. Hennig. Revis. Lamell. i Nilsson's ' Petrif. 



Suecana' (Kou. Pysiogr. SiillsL". i 

 Lund. Handl.,N. F., vol. viii), p. 25. 



1898. — SPINOSUS, G. MiiUer. Mollusk. Untersen. von Braunschweig u. 



Ilsede (Abhandl. d. k. preuss. geol. 

 Land., n. F., pt. 25), p. 23, pi. iv, fig. 4. 



Description. — Shell regular, ovate, slightly inequilateral, 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. 



Eight 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 slightly curving spines, with a 

 groove on their upper surfaces, are borne at intervals by some of the ribs — 

 frequently hj 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 



17 



