SPIRAL ARRANGEMENTS IN ANIMALS 



29 



PLATE XIV 



Fro. 1. 



Fig. 2. 



Plate xiv. illustrates spiral configuration of shells. 



Fig. 1. — A. Rhynchonella •pudtuceit. Shows interior of dorsal valve. Tlie spiral labial apjiendage at the riglit of the figure is 

 coiled and occupies its normal position ; the spiral labial appendage at the left side is uncoiled and di.splaced (after Davidson). 



B. Restored interior of dorsal valve of Uncites gryphus from the Middle Devonian, showing beautiful riglit and left-handed .spirals 

 (after Davidson). 



C. Koninckina leonhardi from the Trias of St. Cassian, enlarged. Displays right and left-handed brachial processes (after Zittel). 



D. Interior of the dorsal valve of Dayia navicula, Silurian, enlarged (after Davidson). Repeats the right and left-handed 

 spiral arrangements seen in A, B, and C. 



E. Macroscaphites ivanii. Cretaceous (Neocomian). 



F. Heteroceras emerici. Cretaceous. 



G. Diceras arietina. Upper Jurassic. 



Figs. E, F, and G display unusual spiral forms, E forming a left and F a right-handed spiral, and G a right and left-handed spiral 

 united. The number and variety of .spirals in shells is incredibly great. 



Fig. 2. — Spiral Foraminifera after Brady. Challenger Reports. Zoology, vol. ix. Tliese shells supply beautiful examples 

 of right and left-handed spirals : also plication and symmetric markings. 



A. Ammodiscun charoides, x 70. D. Gyclammina orbicularis, x 15. G. Coruuspira carinata, x 30. 



B. Polystomella macella, x 35. E. Spirillina Uvibata, x 60. H. Pemropilis pertusus, x 35. 



C. Chilostoniella ovoidea, x 70. F. Cristellaria variabilis, x 50. I. Textularia trochus, x 25. 



