SURFACE FAUNA OF THE GULF STREAM. 3 



floats are thrown upon the beach behind Fort Jefferson at the Tortiigas in 

 o-reat numbers, forming reguLir windrows, and, when dr\-, are blown by the 

 winds to the highest parts of the beach. 



The Florida species is much larger than the Mediterranean V. spiralis, 

 Specimens measuring nearly four inches in leugth are not uncommon. 

 On Plate I is figured in profile, from above and below, a huge Velella, 

 nearly five inches in length. This is a somewhat unusual size. The out- 

 line of the mantle, seen from above, is less elliptical than in V. .sj/iraiis, 

 it is somewhat rectangular, with rounded corners (PI. I, Fig. 2), and 

 is also proportionally broader than in the Mediterranean species. Seen 

 from above (PL I. Fig. 2), the color of the mantle is of a metallic bluish 

 green, with a deep cobalt blue edge surrounding the outer edge of the float, 

 and a similar band, forming an irregular ellipse with re-entering sides, placed 

 somewhat diagonally across the float. Between these bands the color of the 

 mantle passes rapidly from a yellowish green to the dark-blue inner and 

 outer bands. Through the outer edge of the mantle tlie base of the outer 

 blue tentacles of the lower side of the float can be indistinctly seen. The 

 whole of the mantle is dotted with the patches of the so-called liver-cells, of a 

 brownish color. The extreme edge of the dark outer part of the mantle is 

 fringed with a light cobalt blue band, in which are placed the glandular 

 organs of the free edge of the mantle. The free outer edge of the mantle is 

 usually turned down so as to form slight indentations, or apparently sharp 

 incisions in the general outline (PI. I, Figs. 2, 3). The figure from below 

 (Fig. 3) shows how the edge of the mantle is carried when folded under to 

 produce the incisions seen from the upper side. The mantle, where it covers 

 the central part of the float, is of a light greenish blue, with a metallic lustre, 

 with a few patches of liver-cells, diminishing in number towards the base of 

 the keel. The greenish lines of color form concentric lines parallel with the 

 chambers of the float, crossed by triangular radiating rays extending from 

 the fixed edge of the mantle towards the base of the keel, dividing the float 

 into irregular alternating sections of light and colored triangular spaces. 

 The keel is of a delicate steel color, with a thickened edge of the mantle 

 (PI. I, Fig. 2) running round it. In this the patches of liver-cells are closely 

 packed together, and form dark-violet triangular patches, extending at right 

 angles from the edge of the keel to the edge of the mantle. Seen from 

 above the float is divided longitudinally by a long triangular band of liver- 

 cells, which are seen through the float, so as to divide the float into two 



