CYMBULARIA DRUMMUCKENSIS. 67 



without reflexed lateral lips, but with basal corners supported laterally by 

 prominent thickened callosities projecting- horizontally and completely filling 

 umbilicus; outer lip with short, acutely V-shaped sinus followed by long narrow 

 slit extending about one-third the length of whorl; lateral lips forming large 

 gently rounded subparallel lobes with upper edges slightly folded inwards and 

 basal portions thickened to join umbilical callosities. Slit-band narrow, slightly 

 raised, concave between sharp margins. Surface of shell marked with fine regular 

 transverse thread-like lines, closely placed, often minutely fimbriated, curving back 

 rather suddenly at about two-thirds their length to meet slit-band at very acute 

 angles (20°— 30°). 



Dimensions. — Height of shell, 21 mm. ; thickness at umbilicus, 13 mm. 



Horizon. — Drummuck Group (Upper Ordovician). 



Locality. — Thraive Glen, Drummuck, Girvan. 



Remarlcs. — The ck>s< d umbilicus and umbilical callosities projecting laterally 

 resemble members of Perner's group Prosoptychus, but the last portion of the 

 outer whorl is not straightened. The narrow sunken slit-band with raised edges 

 is like Cymbidaria as illustrated by Perner, and the general shape of the shell 

 resembles G. galeata, Koken, and II. fastigiatus, Lindstr., 1 which Koken refers to 

 Cymbularia. In the latter species, judging from Lindstrom's figures, the ornament 

 is closely similar, and so is also the general shape of the shell, but the umbilicus is 

 not closed. However, II. globulus, Lindstr., 2 which Koken himself placed in his 

 genus Cymbularia, has a closed umbilicus, and the basal angles of the mouth are 

 supported on umbilical callosities as in (7. drummuchensis. The American species 

 B. subangularis, Ulrich, 3 may perhaps be compared with our shell, and the 

 imperfectly known II. obtectus, Phillips, 4, from Marloes Bay, of which the type- 

 specimens [28005, 28004] are in the Jermyn Street Museum, undoubtedly bears a 

 great resemblance to it. 



Some specimens of C. drummuchensis from the typical locality and horizon 

 which have a rather more subglobose shape and broader dorsum, with a tendency 

 to trilobation of its surface, may represent a variety. 



It is probable that C. drummuckensis is the Girvan species referred by Salter 5 

 to Sowerby's B. acutus, which is undoubtedly quite distinct. 



The type-specimens of C. drummuckensis are in Mrs. Gray's Collection and 

 come from Thraive Glen. 



1 Lindstrom, ojj. cit., p. 76, pi. vi, figs. 1 — 10. 



- Lindstrom, op. cit., p. 75, pi. v, tigs. 25 — 34. 



3 Ulrich and Scofield, op. cit., p. 920, pi. lxiv, figs. 14 — 16. 



* Phillips, 'Mem. G-eol. Surv.,' vol. ii, pt. i (1848), p. 356, pi. xiv, fig. 12. 



5 Salter, 'Quart. Journ. G-eol. Soc.,' vol. vii (1851), p. 172, pi. ix, figs. 18, 18 a. 



