98 DR. GWYN JEFFREYS ON THE MOLLUSCA OV THE [Mar. 6 



This lovely shell is extremely variable in respect of the height of 

 the spire and the consequent contraction or dilatation of the umbilicus, 

 as well as with regard to the sculpture. I have now examined between 

 200 and 300 specimens of different sizes and ages, and can scarcely 

 find any two of them exactly alike. A remarkable variety which I 

 have named affinis, and at one time believed to be a distinct species, 

 is figured in Plate XX. fig. 5. It is finely and closely reticulated ; 

 the whorls are rounded and show no trace of angularity ; and the 

 umbilicus is not encircled by a keel. The typical or fossil form 

 is usually marked with an irregular row of reddish spots, which are 

 not observable in living specimens. Owing to the variability and the 

 want of sufficient means of comparison, I could not identify our Crag 

 shell with the recent species ; but the opportunity lately afforded 

 me by my friend Prof. Seguenza of inspecting his extensive and most 

 interesting collection of Reggio fossils has now enabled me to connect 

 them. 



9. Trochus ottoi, Philippi. 



T. ottoi, Phil. Moll. Sic. ii. p. 227, t. xxviii. f. 9. 



'Porcupine' Exp. 1869: St. 23; fragments. 1870: All. 16, 17, 

 \1a, off"C. Espichel. 



Distribution. Josephine Bank, Bay of Biscay ('Travailleur ' Exp.), 

 between the Hebrides and Faroes (* Triton ' cruise), Mediterranean, 

 ('Washington' Exp. 1881), St. Thomas, Danish W. Indies ('Chal- 

 lenger ' Exp.), N. England ; 115-1044 fms. 



Fossil. Pliocene : Calabria and Sicily. 



Margarita regalis of Verrill and Smith, Trochus {Margarita) 

 rhysus and T. (Marg.) agleis of Watson, and T. vaillanti of Fischer. 



The American resemble the fossil specimens more closely than 

 those from the European seas ; but the species shows considerable 

 variability as regards the sculpture and umbilicus. The apex or 

 primary whorls ought to be examined in this and all other turbinated 

 Gasteropods as affording a good criterion of distinction. 



So many species of this peculiar and beautiful type have been 

 described by Mr. Watson from the ' Challenger ' Expedition, that 

 they might constitute a distinct section of Trochus equal to that of 

 Margarita. 



B. OxYSTELE, PhiHppi. 



! 10. Trochus euspira, Ball. (Plate XX. fig. 6.) 



Margarita'? euspira, Dall, Bull. Mus. Comp. Zool. 1881, p. 44. 



'Porcupine' Exp. 1870: Atl. St. 16, 17, 17a. Specimens 

 numerous, but dead and few quite perfect. 



Distribution. Culebra I., Danish W. Indies ('Challenger' Exp.), 

 G. Mexico ('Blake' Exp.); 390-805 fms. 



The diameter of my largest specimen is about three tenths of an inch 

 or 9 millimetres. This pretty shell is extremely variable as regards 

 the height of the spire and the sculpture. Some specimens are 

 quite smooth ; others are spirally striated throughout, or on the 



