Sutek. — A New Placostylus from Neto Zealand. 343 



The anatomy of P. hongii has been ably described and figured 

 by Mr. B. Murdoch in Proc. Mai. Soc, vol. iii, p. 324, pi. 16, 



P. bollonsi is distinguished from all the other species of the 

 genus known to me by the obtuse, broadly rounded apex. In- 

 teresting features are the costate, very rarely punctate proto- 

 conch, and the loss of the spermatheca. As I pointed out in 

 my paper on P. hongii ambagiosus (Journ. de Conch., vol. liv, 

 p. 255), it is very' likely that during the Pliocene a form closely 

 allied to P. bivaricosus solidus, Eth., spread from Lord Howe 

 Island southward, and that from it was derived P. hongii am- 

 bagiosus, and from this again the more simple form of P. hongii. 

 We may not be very far from the truth if we assume that P. 

 hongii and P. bollonsi are the offsprings of a common ancestor, 

 and we may look upon the Great King species as a splendid 

 example of the originating of a new species by isolation. 



It gives me very great pleasure to unite the name of the 

 discoverer of this interesting and fine shell with the species. 



Since writing the above Captain J. Bollons has revisited 

 the Great King Island, and to his unremitting kindness I am 

 indebted for an egg and embryonic shell of P. bollonsi. As 

 was to be expected, the egg is very large, elongately regularly 

 oval, rounded at both ends, calcareous, thin, white, finely granu- 

 lar, with a few larger granules irregularly interspersed ; its 

 length is 18 mm. ; diameter, 13 mm. Compared with the 

 egg of P. hongii, which measures 7 mm. by 5| mm., it is a real 

 giant. The egg of Paryphanta busbyi is 13 mm. by 11mm. 

 The embryonic shell, of 3J whorls, is axially finely ribbed, and 

 on the upper half of the last whorl the riblets are decussated 

 by fine spiral lirae. There is a distinct, narrow, and open um- 

 bilicus. Height, 17 mm. ; diameter, 12 mm. ; height of aperture, 

 13 mm. 



EXPLANATION OF PLATE XXV. 



Figs, a, b. Placostylus bollonsi, Suter. Type specimen. 

 Fig. c. ,, „ Specimen showing the reticulated 



sculpture. 



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