I T ROSALPINX. 153 



weeks. The vases are generally attached in more or less regu- 

 lar rows, covering sometimes an area of three or four square 

 inches. In shape and size they are like the egg-cases of Purpura, 

 but without the slight reddish tinge of the latter. They are 

 flattened vertically, and their edges are marked by keel-like 

 ridges. Owing to the lengthened period of oviposition, eggs and 

 embryos in all stages of development are to be found in the 

 various vases of a group, and the young escape from the first- 

 laid vases before the female has finished laying. Unlike the 

 vases of Purpura, each of which contains several hundred eggs, 

 those of Uroxalpiii.r contain only from six to twenty, ten or 

 twelve being the usual number. All of these normally undergo 

 development, and give rise to embryos. Occasionally a partially 

 segmented egg or more advanced embryo becomes abortive and 

 breaks up into separate cells, each of which remains alive for 

 some time, and often swims actively by the motion of its cilia. 

 These cosmelhe and the yolk of the aborted eggs are drawn into 

 the digestive cavities of other embryos, but this method of fur- 

 nishing the young with food is exceptional and accidental, 

 although normal in the Purpunie.* 



Reeve (Monog. Fusus) has figured JEupleura Tampaenzis, 

 Conrad, in mistake for this species. Fiisus recur vus, Koch (fig. 

 487), appears to be a small specimen of U. cinerea. 



II. FLORIDANA, Conrad. PL 39, fig. 48G. 



Distinguished from U. ciyerea mainly by its shouldered whorls, 

 the ribs forming nodulous projections at the angles. Cinereous, 

 not banded ; purple within. Length, 1*2;> inches. 



Florida . 



U. MEXICANA, Reeve. PL 39, fig. 482. 



" A neatly sculptured species, distinguished by the light yel- 

 lowish color of the ridges upon a purple-brown ground. n 



Length, '9 inch. 



Mexico. 



This may prove to be identical with U. Floridana, and if so, 

 will have priority over that species. 



* W. K. Brooks, in "Scientific Results, Chesapeake Zoological Labora- 

 tory," 121, 1879. 



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