948 ON FOSSIL CIRRIPEUES. 



fossil species that can be definitely referred to Calantica (Scillce- 

 le'pas) are found in Tertiary rocks, viz. Scillcelepas paronce 

 from the Miocene of the neighbourhood of Turin, Italy, and 

 S. carinata and S. ornata from the Pliocene of Messina, Sicily, 

 so that it is an important adv^ance to show that a representative 

 of the genixs existed so far back in time as the Cenomanian. It 

 is certainly remarkable to find that T. tuherculata had a more 

 highly specialized scutum than the Tertiary and recent species, 

 and to mark this advance in the evolution of the group, I place 

 it in a new sub-genus, Titanolepas. This course is the more 

 desirable since T. tuherculata may represent a side line of develop- 

 ment from the ancestral Scillcelepas line, which, by the sup- 

 pression of the lower whorl of valves, and by the umbo of the 

 carina becoming sub-central, may eventually have given rise to 

 the genus Oocynaspis. 



For help in connection with this paper, I wish to express my 

 indebtedness to Dr. F. A. Bather, Dr. W. T. Caiman, Mr. C. P. 

 Chatwin, and Dr. H. A. Pilsbry. 



EXPLANATION OF THE PLATES. 



All the specimens here figured are in the collection of the Geological 

 Department of the British Museum. 



Plate XCIV. 



Zeugmatolepas mocMeri Withers, gen. et sp. ti. 



Fig. 1. Carina. Cenomanian, Chalk Mnrl : near Cambridge. I. 15820. a, outer 

 view ; b, side view ; c, inner view. 



2. Carina, L 15821. a, outer view; 6, side view ; c, inner view. 



3, 4, 5, 6. Scuta (various forms), I. 15822-1. 15825. "| 



7. Tergum, I. 15826. I «, outer view ; b, inner 



8. Upper latus, 1. 15827. f view. 



9. Eostrum, L 15828. J 



10. Several valves in position, includilig the cai'ina, I. 15829. 



11. Holotype. Nearly complete capitulum showing the left side, I. 15830. 



12. Several valves in position, 1. 15831. 



13. Nearly complete capitulum showing the right side, I. 15832. 



14. Restoration of capitulum based on the above material from the Chalk Marl 



of Cambridge, c, carina; s., scutum; ^., tergUm; «./., upper latus; 

 r., rostrum; ?. Z., lower latera ; s.c, sub-carina. 



Figs. 1, 2, 4, 9-13, X 10 diameters; figs. 3, 5-8, 14, X 5 diameters. 



Plate XCV. 



Calantica {Titanolepas) tubercidata Darwin sp. 



Fig. 1. Carina. Cenomanian, Chalk Marl : near Cambridge. I. 15842. a, outer 

 view ; b, side view ; c, inner view ; d, transverse section near apeX. 



2. Scutum, L 15843 (figure reversed). ") 



3. Tergum, I. 15844. I 



4. Rostrum, I. 15845. | 



5. Rostral latus, I. 15846. Y a, outer view ; b, inner view. 



6. Median latus, I. 15847. 



7. Carinal latus, I. 15848 (figure reversed). | 



8. Sub-carina, I. 15849. J 



9. Carina and pair of terga in position. [? Cenomanian] Chalk detritus; 



Charing, Kent. I. 14656. 

 10. Restoration of capitulum, based on disconnected valves from the Chalk Marl 

 of Cambridge, c, cai'ina; s., scutum; t., tergum ; r., rostrum : r.l., rostral 

 latus; m.?., median latus; c.i., carinal latus; s.c, sub-carina. 



Figures 1-10 X 10 diameters. 



