MUSEUM OF COMPARATIVE ZOOLOGY. 291 



names, but the shells show no differential characters. A fine specimen in the 

 Museum, from the Miocene silex-beds of Tampa, Florida, was carefully cleaned 

 of all its load by a youthful assistant, under the impression that he was 

 relieving the fossil from extraneous matter ! 



Section TUGURIUM P. Fischer. 



Xenophora caribeea Petit. 



Xenophora caribcea Petit, Journ. de Conchy liologie, V. p. 248, pi. x. figs. 1, 2, 1856. 



Habitat. Stations 12, 32, and 36, in the Gulf of Mexico, in 36-95 fms.; 

 Station 156, off Montserrat, in 88 fms.; Station 174, off Guadelupe, dead, in 

 878 fms. ; Station 300, near Barbados, in 82 and 100 fms.; bottom temperatures 

 60°-69° F. U. S. Fish Commission in the Gulf of Mexico and Antilles, in 

 14-274 fms., living, and northward to the vicinity of Cape Hatteras, in 30-40 

 fms., usually on a muddy bottom. 



This species arranges small shells, usually bivalves, in a fringe around the 

 marginal lamina. One specimen from very deep water had appropriated several 

 small pieces of coal thrown overboard with ashes by some steamship. The 

 open umbilicus is frequently occupied by a tubicolous annelid, which lives 

 in good fellowship with its involuntary host. In this species the habit of 

 cementing shells to its margin is evidently merely a habit, as the projecting 

 shells must be inconvenient in moving about, and have no protective value. 

 The practice is a reminiscence of a time when it was really useful, and Ave can 

 assume with confidence that this species is of later development and origin 

 than the preceding one. 



The separate objects appear to be selected with a certain taste and care, as 

 they are usually of nearly the same size, separated from one another by about 

 the same space, and the convex side of the object is always downward. 



The soft parts are small in proportion to the shell, whitish, with large eye8 

 and long tentacles. In alcohol the opercular lobe is larger than the foot. The 

 operculum is more lozenge-shaped than that of A', caperata as figured by Petit, 

 and the nucleus is less central. The operculum is smooth outside, with an 

 obscure central rib on the base, and striated both ways on that side. 



It is worthy of note that the operculum of A', caperata Phil, resembles that 

 of X. conchy! iophora in being subsymmetrical and subtriangular, while that of 

 the present species is asymmetrical. If this feature holds good, it would add 

 another to the characters by which the two sections of the genus may be 

 separaLcd. 



From the appearance of a number of specimens of this species, I have been 

 led to suspect that, when young, the animal may have the power of extruding 

 a purplish fluid, not unlike that of Trophon and some other gastropods. 



On dead fragments of this species were found nearly all the specimens of 

 Dimya dredged by the Blake, and they afford an excellent perch for the ser- 

 pulse, sertularians, and polyzoa which inhabit the depths. 



