LIST OF ILLUSTRATIONS xiii 



FIG. ^ PAGE 



281. A shell' of Macroscaphitps, to shew change of curvature . . 550 



282. Construction for determining the length of the coiled spire . . 551 



283. Section of the shell of Triton corrugatus (Woodward) . . . 554 



284. Lamellaria perspicua and Sigaretus halioioides (do.) . . . 555 



285. 6. Sections of the shells of Terebra maculata and Trochus nilolicvs 550. (iO 

 287-9. Diagrams illustrating the lines of growth on a lamellibranch shell 563-5 



290. CaprineUa adversa (Woodward) ....... 507 



291. Section of the shell of Productus (Woods) ..... 567 



292. The "skeletal loop" of Terehratula (do.) 508 



293. 4. The spiral arms of Spirifer and of Atrypa (do.) .... 5(i9 

 295-7. Shells of Cleodora, Hyalam and other pteropods (Boas) . . 570, 1 

 298, 9. Coordinate diagrams of the shell-outline in certain pteropods . 572,3 



300. Development of the shell of Hyalaea tridentata (Tesch) . . . 573 



301. Pteropod shells, of Cleodora and Hyalaea, viewed from the side (Boas) 575 



302. 3. Diagrams of septa in a conical shell 570 



304. A section of Nautikis, shewing the logarithmic spirals of the septa to 



which the shell- spiral is the evolute . . . . .581 



305. Cast of the interior of the shell of Nautilus, to shew the contours of 



the septa at their junction with the shell-wall . . . 582 



306. Ammonites Soinerhyi, to shew septal outlines (Zittel, after Stcinmann 



and Doderlein) 584 



307. Suture-line of Pinacoceras (Zittel, after Hauer) .... 584 



308. Shells of Hastigerina, to shew the "mouth" (Brady) . ■ . 588 



309. Nummulina antiquior (V. von Moller) ...... 591 



310. Cornuspira foliacea and Operculina complanata (Brady) . . . 594 



311. Miliolina pulchella and liiuiaeana (Brady) ..... 596 



312. 3. Cyclammiria cancellata (do.), and diagrammatic figure of the same 596, 7 



314. Orhulina universa (Brady) ........ 508 



315. Cristellaria reniformis (do.) ........ 600 



316. Discorhina hertheloti (do.) ......... 603 



317. Textularia trochus and concava (do.) ...... 604 



318. Diagrammatic figure of a ram's horns (Sir V. Brooke) . . . 615 



319. Head of an Arabian wild goat (Solater) 616 



320. Head of Ouis Ammon, shewing St Venant's curves . . . 621 



321. St Venant's diagram of a triangular prism under torsion (Thomson 



and Tait) 623 



322. Diagram of the same phenomenon in a ram's horn . . . 623 



323. Antlers of a Swedish elk (Lonnberg) 629 



324. Head and antlers of Cervus duvauceli (Lydekker) .... 630 



325. 6. Diagrams of spiral phyllotaxis (P. G. Tait) .... 644, 5 



327. Further diagrams of phyllotaxis, to shew how various spiral appear- 



ances may arise out of one and the same angular leaf-divergence 648 



328. Diagrammatic outlines of various sea-urchins ..... 664 



329. 30. Diagrams of the angle of branching in blood-vessels (Hess) . 667,8 

 331, 2. Diagrams illustrating the flexure of a beam .... 674, 8 



333. An example of the mode of arrangement of bast-fibres in a plant-stem 



(Schwendener) .......... 680 



334. Section of the head of a femur, to shew its trabecular structure 



(Schafer, after Robinson) ....... 681 



