LEPTOMEDUS.E — BLACKFORDIA. 277 



Halopsis (Mitrocoma) cruciate, 1865 (North Amer. Acal., p. 102, figs. 151, 152). Dr. Agassiz, 

 however, describes cirri upon the bell-margin between the tentacles in H. cruciata, and states 

 that there are but 12 marginal sense-organs, 3 in each quadrant. In Blackfordia there are no 

 cirri and the marginal sense-organs are very numerous. Blackfordia is distinguished from 

 Phtaluaum and Phtalopsis by the absence of permanently rudimentary tentacles or cirri. 



The medusae of Blackfordia are also quite similar to Tiaropsis in the appearance of the 

 manubrium and general shape of the bell, but in Tiaropsis there are but 8 marginal sense- 

 organs and the entodermal cores of the tentacles do not project inward into the gelatinous 

 substance of the bell, as in Blackfordia. 



The type species is Blackfordia manhattensis, found off the coast of New Jersey, United 

 States. 



Blackfordia manhattensis, sp. nov. 



Plate 36, figs. 2-2"'. 



Bell 10 mm. in diameter, higher than a hemisphere, with relatively flat, sloping sides and 

 bluntly rounded apex. Bell-cavity about half as deep as bell-height. 70 to 80 slender ten- 

 tacles with short, blunt, basal bulbs. The tentacle-bulbs give rise each to a finger-shaped 

 entodermal diverticulum, which extends upward into the gelatinous substance of the bell. 

 There are usually 2, and sometimes 3,lithocysts between each successive pair of tentacles; the 

 lithocysts contain 2 to 5 spherical concretions, the large lithocysts having almost invariably 

 5 concretions. There is no black pigment at the base of the lithocysts, as in Blackfordia 

 virginica. There are 4 straight, narrow radial-canals and a slender circular vessel. Velum 

 well developed. The manubrium is quadratic in cross-section and about half as long as 

 depth of bell-cavity; it is provided with 4 very long, slender, frilled lips. The gonads are 

 found on the middle parts of the radial-canals and are irregularly flexed, sinusoidally, from 

 one side to the other of the canal. 



Entoderm of manubrium sage-green; that of tentacles and gonads lighter in color, being 

 almost milky. 



This medusa is common off Sandy Hook and other parts of the coast of New Jersey in 

 October. 



Blackfordia virginica sp. nov. 



Plate 36, figs. 3-5; plate 37, fig. 6. 



Mature medusa (plate tf, fig. 6). — Bell 14 mm. wide, somewhat higher than a hemisphere, 

 with relatively straight, sloping sides and rounded apex. There are about 80 long, slender 

 tentacles, capable of much contraction; tentacle-bulbs short and swollen. A finger-shaped 

 entodermal projection extends upward from some of the tentacle-bulbs into the gelatinous 

 substance of the bell. In some medusas only about one-quarter of the tentacles display these 

 diverticula, in others it is exhibited by fully three-quarters of the tentacles. There are usually 

 1, rarely 2, lithocysts between each successive pair of tentacles. Each lithocyst contains typi- 

 cally 2, but occasionally3 or more spherical concretions. The entoderm of the bell-rim at the 

 bases of the lithocysts contains dense-black pigment-granules. Bell-cavity about half as deep 

 as bell-height. Velum large. 4 straight, slender radial-canals. Manubrium quadratic in 

 cross-section, flask-shaped, with recurved and prominently fluted lips; it extends about half 

 the distance from inner apex of bell-cavity to velar opening. Gonads linear, extending from 

 radial corners of stomach over somewhat more than half the length of the radial-canals. The 

 eggs of female protrude from the surface of the ectoderm and are cast off one by one (plate 



36, %• s)- 



The entoderm of the tentacle-bulbs and gonads is dull milky-yellow, while that of the stom- 

 ach is often of a delicate green. 



When the medusa is 0.8 mm. in diameter the bell is higher than a hemisphere, with thin 

 flexible walls. There are 8 tentacles and 8 lithocysts, each containing 1 or 2 spherical concre- 

 tions, one concretion being usually larger than the other. Lips only slightly recurved and not 

 fluted. There are as yet no gonads and no black pigment in the entoderm of the bell-rim. 

 This black pigment begins to develop when the medusa has 16 tentacles and the bell is hemi- 

 spherical and 1.7 mm. in diameter. 



