360 T. Mellard Reade—Pehhle- Ridges. 



conical helix. Hydrothecas 40 to the inch, subtriangular in form, 

 with curvilinear margins ; aperture terminal ; denticle prolonged in 

 a well-marked spine. 



Our specimens of this species are all very small, the great 

 majority of examples being less than one inch in length. They 

 are usually compressed so as to present the appearance figured on 

 Plate XIIL Fig. 6&. 



This species is recognized at once by its small size, characteristic 

 curvature and conspicuous apertural spines. 



Locality. — It occurs rarely in the highest bed of the Birkhill 

 Shales at Dobbs Linn, Whitehope, Frenchland, etc., and in the Gala 

 Group at Meigle Hill, Buckholm, Elwand Burn, Cowdenknowes, etc. 



Fj(.s_ explanation of plate XII. 



la—/ Monograptus Hisingert, Carr., typical form, la — \d. distal portion; lb. 



proximal end. Grieston Quarry. Ic. Id. adult portion ; oblique view. 



Elliotsfield. 1^. 1/. adult fragment. Long Sleddale, Westmorland. 

 2a — d Monograptus, Yar. faculum,'Lsi^'w. 2a. proximal; 2b. distal portion; 2c. 



characteristic view ; 2 ^. in relief. Dobbs Linn. 



3 a — d Monograptus cgphus, Lapw. 3 a. adult ; 3 b. proximal portion ; 3 c. in 



relief ; 3 d. near proximal extremity. Dobbs Linn. 



4 a — e Monograptus leptotheca, Lapw. 4 a. adult portion ; 4 b. central ; 4 c. 



proximal ; 4 d. impression ; 4 e. cast. Dobbs Linn. 



5 a — d Monograptus Galaensis, Lapw. 5 a — c. distal ; 5 b. d. proximal extremity. 



Galashiels. 



6 a — d Monograptus vomerinus, Nich. 6 a. nat. size ; 6 b. compressed centrally ; 



6 c. characteristic view ; 6 d. oblique view. Elliotsfield. 



-pj^g EXPLANATION OF PLATE XIIL 



1 a — d Monograptus Salli, Barrande. 1 a. distal ; 1 b. proximal portion ; 1 c. 



flattened ; Id. in relief. Mountbenger Burn. 



2 a — c Monograptus Riccartonensis, Lapw. 2 a. b. distal portion in partial relief. 



Teiveshilly, County Down. (Coll. W. A. Swanston, Esq.) 2c.d.e. 

 Elliotsfield. 

 3« — d Monograptus SedgwicJcii, Portlock. 3a. b. distal portion; 3. c. d. proximal 

 end. Sundhope. 



4 a — h Monograptus convolutus, His. 4 a. b. var. communis, 4 c. d. yox.Jimbriatus. 



Dobbs Linn. ^e.f. var. proteus. Coal-pit Bay. ^g. h.YOx. spiralis. 

 (Coll. Prof. Nicholson.) Dobbs Linn. 



5 a — b Monograptus triangulatus, Harkness. Dobbs Linn. 



6 a — b Monograptus turriculatus, Barrande. Elwand Bank, Galashiels. 



IV. — Pebble Ridges. 

 By T. Mellakd Beade, C.E., F.G.S. 



AS a contribution to our knowledge of the formation of these very 

 interesting " natural embankments of the sea," 1 may point 

 to a little bay in Anglesea, immediately westward of the Bryn Ddu 

 Limestone quarries on the north-east coast of Anglesea, about two 

 miles and a half westward of Puffin Island. This little bay is not 

 more than about a furlong across, and may be roughly described as 

 semicircular in form, lying nearly due west to east from point to 

 point. From being in miniature as it were, the ridge can be readily 

 studied, and it is very striking to see how, commencing in the west- 

 ward as a beach, it gradually rises into a ridge having very steep 

 sides. No less remarkable is the way in which the stones increase 



