56 J. W. Judd—On Volcanos. 



ribs are nearly obsolete. The form of their spires is also not 

 pupseform. The shell measures without canal -017, canal only -022. 



Distribution. — Gault of Folkestone, where it is rare. 



I should perhaps have named this A. pupaformis, and have 

 thereby implied the form and character of the shell ; but this name 

 was appropriated by D'Archiac in 1847 for a little-known Oolitic 

 species. I have named it in compliment to John Griffiths, the well- 

 known collector at Folkestone, who has furnished me with the great 

 majority of my specimens. A comparison of specimens in cabinets 

 supplied by him with figures of Folkestone fossils of twenty or 

 thirty years ago, shows the useful, and let us hope not unprofitable, 

 work he has devoted himself to. 



EXPLANATION OF PLATE III. 



Fig. 1. — Aporrha'is retusa, J. Sby. Natural size, showing ventral side. The posterior 



digit is slightly lengthened from a specimen lent me hy Mr. Price. 

 Fig. 2. — Showing dorsal side. 

 Fig. 3. — Specimen showing dilated lip. 

 Fig. 4. — Part of a shell, to show dilated node. Enlarged. 

 Fig. 5. — A young shell, to show mode of growth. 



Fig. 6. — A young shell, illustrating the same, from the British Museum. 

 Fig. 7. — Aporrha'is cingulata, Pictet and Roux, showing arrangement and relative 



position of digits and canal. 

 Fig. 8. — Specimen showing development of wing. 

 Fig. 9. — Another, with dorsal view. 

 Fig. 10. — Specimen showing aperture and middle digit. 



By tracing and reversing Fig. 7 and Fig. 8 an illustration can be 

 obtained of the relative length and position of the wing and canal, 

 showing general appearance of the shell. 

 Figs. 11 to 14. — Aporrha'is Griffithsii, Gardner, from Folkestone. 



All in the author's cabinet, save Fig. 6. 

 Fig. 15. — Aporrha'is pes-carbonis, Recent. 



(To be continued.) 



II. — Contributions to the Study of Volcanos. 



By J. W. Judd, F.G.S. 



[Continued from page 16.) 



The Lipabi Islands {continued). 



3. Third Period of Volcanic Activity in the Lipari Islands. 



Although, as we have already seen, the older volcanic formations 

 of the Liparis present us with features of no little interest, yet it 

 is on account of the cones and lava-streams, composed of rocks of 

 singular beauty and almost unique character, — which are the product 

 of the latest developments of igneous action in these islands, that 

 the attention of geologists is most frequently directed to them. 



Lofty cinder-cones, composed of snowy pumice, their vast craters 

 breached by lava-streams of solid glass, seemingly fresh as when 

 the fiery flood leaped from the volcano's throat, and poured with 

 slow and tortuous current down its flanks; wide-spreading lava- 

 fields, their horrid bristling surfaces coated by a reddish-brown 

 crust, but exposing in grand cliff-sections the most marvellous com- 

 binations of variegated rocks ; — these seen rising amidst the bright 

 blue waters of the Mediterranean, and displayed in that clearness of 



