30 PliOCKKDINGS OF THE M A LACOLOGICA I, SSOCIKIY. 



EuDOXocuiioN IMITATOR, n.sp. PI. I, Figs. 5, 7, 9. 



Sliell large, oval, depressed; valves slightly keeled, siiie slopes 

 straight, girdle leatherj- with short spinelets. General coloration 

 uniform dark-brown, girdle pale greenish-brown. Sculpture as in 

 preceding species. Contrasted with the foregoing species the valves 

 are more depressed, posterior valve with mucro planate, almost central. 

 Inside coloration pure white. Sutural laniinre longer than in the 

 above species, and the sinus even less pronounced. Insertion-plates 

 longer, and the anterior valve with more than twenty-tive teeth, tlie 

 posterior about twenty-two. (jlirdle leathery, with short brown 

 spinelets. Length of type 59, breadth 40 mm. 



Ilab. — Sunday Island, Kermadec Group. 



Station. — On rocks below low tide. 



" Eudoxocliiton is endemic in JS^eozelanic waters with two distinct 

 species. E. nobilis, Gray, lives on the surf-swept boulders, and its 

 form and internal characters are well suited to withstand the force of 

 the waves. £. Jmftoni, Pilsbry, is easily separated by its much more 

 depressed form and longer teeth, it is only found on the most exposed 

 situations, and would appear to be mucli rarer. Which is the parent 

 or to which would the parent form be more like would be difficult to 

 suggest. The question is more complicated by tlie finding on Sunday 

 Island of two forms of Eudoxochiton. . . . The Eudoxochitons of 

 Sunday Island are very puzzling, as the existence of two forms on 

 such a small island I could scarcely credit myself. Yet the shells 

 seem easily separable into two lots, which might be classed as varieties 

 of nohilis, Gray ; they differ in general form as much from each other 

 as from that species and are both less elevated. One form is even 

 lower than Imttoni, Pils., tliough in the characters and number of the 

 teeth it absolutely agrees M'ith the other. I have so tar been unable 

 to provide a satisfactory explanation tor the differentiation of these 

 from each other and from the Eudoxochitons of New Zealand." 



Remarks. — I have here admitted the two forms above indicated 

 as distinct species, and would fully note the differences observed. 

 E. 'perple.TCus was tirst collected, and it was noted as being less elevated 

 than E. iiohiliK (Gray), though quite unlike E. Imttoni, Pilsbry. 

 Collectors of Eudoxochiton well know the rarity of the genus, and 

 veiy few specimens were obtained. Valves were not uncommonh* 

 met with on the beach, and examination of these constantly gave the 

 number of slits in the interior and posterior valves as about twentj-- 

 two or twenty-three. The notes I had with me (copied from 

 Pilsbry) gave — 



E. nobilis, Gray, anterior valve 30 slits ; posterior 24-5 slits. 

 E. huttoni, Pilsbry .. .. 17 ,, ,, 19 



This seemed to indicate that the Kermadec shell was not nobilis 

 (I had not specimens with me for actual comparison), and it was 

 certainly not huttoni. 



In the winter the sand moved along the north coast and forced 

 a large number of Eudoxochiton to come up to low-water mark. This 

 unexpected opportunity was greedily seized to collect every specimen. 



