2-18 BULLETIN OF THE 



operculum is identical, the shell characters shade indefinitely into one another 

 from one specimen to another, the soft parts differ in nothing, the texture, 

 character, color, and habitat of the shells are the same. 



In considering such animals as are given to parasitism or commensalism, it 

 is a truism that we must expect great variations of parts which in non-parasitic 

 species would be of high systematic importance, and, secondly, great variation 

 as between individual specimens of the species. Furthermore, if we have 

 certain individuals of the species which take on a parasitic habit, and others 

 which, whether voluntarily or perforce, do not, we shall find the nearest 

 approach to the perfect norm of the species in the non-parasitic specimens. 



Now, it is the writer's opinion that such forms as have been figured and 

 described as Latiaxis elegans, cariniferus, and Deburghiie in Sowerby's Thesau- 

 rus are merely the most perfect and luxuriant development of a species which, 

 in its parasitic individuals, presents us with forms superficially very different, 

 stunted, modified, or deteriorated. The operculum of Coralliophila galea of 

 authors is precisely that of Latiaxis Dcburghice, and of Rhizocheilus madrepora- 

 rum of Sowerby. The loss of the operculum and other modifications exhibited 

 by the type species of Rhizocheilus are exactly what we might expect in a 

 species in which degeneration and specialization have proceeded very far from 

 long continued parasitism. Still, I should expect to find an operculum in the 

 free young of R. antipathicus. The form of the Antipathes upon which it 

 lives is so slender that the shell must submit to greater changes in form than 

 a species like Coralliophila madreporarum, which habitually rests upon a broad 

 pillar of coral, or like Coralliophila bracteata (Brocchi) Tryon, which rarely does 

 so, but is genei'ally found free. Owing to these modifications, we may retain 

 Steenstrup's name in a sectional sense, as it cannot (though of earlier date) 

 be fairly applied to typical Coralliophila. In so variable a group, it goes with- 

 out saying that the specific determinations are very difficult to make with 

 confidence, and are here made with all reserves. 



Coralliophila Deburghise Keeve. 



Plate XVI. Fig. 5. 



Latiaxis Deburghia: Reeve, P. Z. S. 1857, pi. xxxviii. figs. 3, 6 ; Sby., Tlies. Conch. 

 Latiaxis, No. 2, fig. 5, 1882. 



Habitat. Sigsbee, off Havana, in 80-119 fms. ; Barbados, 100 fms.; Stations 

 164 and 166, off Guadelupe, in 150 fms., hard bottom, temperature 59°. 75; 

 Station 134, off Santa Cruz, in 248 fms., sand, bottom temperature 54°. 5; Sta- 

 tion 174, off Guadelupe (living), in 878 fms., bottom temperature 39°. 75; 

 Station 262, off Grenada, in 92 fms., sand, bottom temperature 62°; Station 

 292, off Barbados, in 56 fms., sand, bottom temperature 74°. 5 F. Northward 

 to Hatteras, U. S. Fish Commission. 



The extraordinary range in depth and temperature which this animal sustains 

 will be remarked. The largest and most foliaceous specimens are from the 



