106 Dr. C. Davmn—BrUidi Earthquakes, 1893-99. 



the outer whorl near the aperture become slightly swollen, and 

 then are suddenly depressed to the level of the marginal groove, 

 the ventral side at the same time considerably narrowing and 

 losing its overhanging edges and being produced apparently into 

 a pointed rostrum. Septa, sutures, and siphuncle not preserved. 



Measurements. — Diameter of shell, 13"-15" ; height of mouth, 

 41"; width of ditto, 11". 



Eemarks. — The only species which has a general resemblance 

 in possessing transverse plications and an overhanging concave 

 ventral side is Gyroceras {Trigonoceras) aigoceras (Miinster),^ but 

 as it consists of only two whorls, which are not in contact, are 

 of much greater breadth, and have a sharp keel-like dorsal side, 

 the resemblance is not very close. Moreover, so far as we know, 

 the mouth did not possess the important features which we find in 

 the Manx form. There is no species of Gyroceras with which I am 

 acquainted exhibiting these characteristics, and it seems impossible 

 to attribute our new form to this genus or to Discites. Pleuro- 

 nautilus has a closely coiled shell with transverse ribs ; but, on 

 the other hand, a rather large central perforation is present. 

 Mojsisovics- has remarked on the relations between G. aigoceras and 

 Pleuronautilus, and it seems advisable for the present to place 

 our new form in the latter genus, though probably a subgenus or 

 genus will have to be made to contain it (which might appropriately 

 receive the name of Mibonioceras from the ancient name of the Isle 

 of Man). Until we know the suture-lines, septa, and siphuncle it 

 will, however, be wiser to associate it with Pleuronautilus. 



EXPLANATION OF PLATE VI. 



Pleuronautilus ? scarlettensis, sp. nov. Carboniferous Limestone : Scarlett Quarry, 



Isle of Man. One-third nat. size. 



1. Body-chamber of shell. 



2. Part of outer whorl. 



3. Inner whorls of shell. 



4. Cast of surface. 



5. Transverse section of Fig. I near the mouth at a. 



6. Transverse section of Fi^. 1 at h. 



III. — On some Minor British Earthquakes of the Years^ 



1893-1899. 

 By Charles Davison, Sc.D., F.G.S. 



DUEING the seven years 1893-1899, 42 earthquakes have been felt 

 in Great Britain— 28 in England and Wales and 14 in Scotland.^ 

 All of the latter number visited areas which are thinly populated, 

 and it has therefore been impossible to draw the boundaries with the 

 accuracy that is to be desired. In the English earthquakes this 



1 Miinster, " Cyrtoeera aigolceros (1838) " : Beitr. r. Petrefact., 2nd ed.. Heft i 

 (1843), p. 56, t. i, figs, la, Ih ; t. ii, fig. 1. Foord : Cat. Foss. Ceph. Brit. Mus., 

 pt. ii (1891), p. 72, and references. 



2 "Die Ceph. d. Medit. Triasprov." : Abhandl. d. k. k. geol. Eeichs., Bd. x 

 (1882), p. 73. 



3 The cost of investigating all these earthquakes was defrayed from grants which. 

 I had the honour to receive from the Government Eesearch Fund. 



-J 



