20 THE VOYAGE OF H.M.S. CHALLENGER 



very slight compression between the back and the belly of the shell. It is thin, brilliant, 

 scarcely opaque, white. Sculpture: There is none, except perhaps some very faint 

 microscopic traces of longitudinal texture. Mouth rather small, very oblique ; edge 

 thin, but not chipped. Apical opening small, straight across the shell, thin, chipped. 

 L. 0-12 in. B. at mouth 001 ; at swelling 0'02 ; at apex 0-009. 



This differs from Cadulus rastridcns, Wats., in being less bent, less swollen, the swelling more central, 

 more apparent on the convex curve ; the shell is less attenuated posteriorly, and more so anteriorly ; there 

 is no transverse sculpture ; the mouth here is oblique, the shell at the anal opening is not thickened, 

 and both ends are narrower. Than Cadulus gracilis, Jeffr., this is much smaller, more attenuated, 

 has a gibbous swelling, and not a mere equable enlargement, and has both openings much 

 smaller. 



From Cadulus jeffreysi, Monter., it differs still more strongly in these very respects, except that 

 in size it is nearer. 



Dall (" Blake " Expedition, Bull. Mus. Comp. Zool. Camb. Mass., 1880, p. 36) quotes this 

 species from three stations in the Gulf of Mexico ; but from examination of a specimen of his species, 

 which he kindly forwarded to me, I am able to say with confidence that it is not Cadulus sauridens. 



5. Cadulus gracilis, Jeffreys (PI. III. fig. 5). 



Cadulus gracilis, J. Gwyn Jeffreys, "Valorous" Moll., Ann. and Mag. Nat. Hist., ser. 4, vol. xix., 

 1877, p. 157. 

 ,, ,, J. Gwyn Jeffreys, "Lightning" and "Porcupine" Moll., Proc. Zool. Soc. Lond., 



1882, p. 664, sp. 3, pL xlix, fig. 7. 



Station 75. July 2, 1873. Lat. 38° 38' N., long. 28° 28' 30" W. 450 fathoms. 

 Volcanic mud. 



Station 78. July 10, 1873. Lat. 37° 26' N., long. 25° 13' W. Off San Miguel, 

 Azores. 1000 fathoms. Volcanic mud. 



Station 85. July 19, 1873. Lat. 28° 42' N., long. 18° 6' W. Canaries. 1125 

 fathoms. Volcanic mud. 



Dr Jeffreys got one specimen in the " Valorous " at Station 13, 690 fathoms. He was good 

 enough to verify my determination of this species. It is very like Cadulus jeffreysi, Monter., but 

 is larger and a little compressed (in the proportion of j^) between the convex and concave curves as 

 compared to its breadth, which is not the case in Cadulus jeffreysi. It is not so swollen, and the 

 posterior opening is larger than in that species. 



6. Cadulus simillimus, Watson (PI. III. fig. 6). 



Cadulus simillimus, Watson, Prelim. Report, pt. 2, Journ. Linn. Soc. Lond., voL xiv. p. 526. 



Station 185b. August 31, 1874. Lat. 11° 38' 15" S., long. 143° 59' 38" E. Raine 

 Island, Cape York, N.E. Australia. 155 fathoms. Coral sand. 



