MUSEUM OF COMPARATIVE ZOOLOGY, 277 



At the extremity of each chyniiferous tube on the bell margin springs a 

 long tentacle, which is commonly carried tightly coiled about the tentacular 

 bulb. On the bell margin, between each pair of long tentacles, are three short 

 tentacular appendages, which are generally more or less coiled around their 

 bases, and are carried upright, as shown in the figure. There are no otocysts. 

 The coloration of the genus was not observed. 



Tiaropsis diademata, Agassiz. 



Plate VII. Figs. 13 14. 



A larval stage of this medusa, younger than any Tiaropsis yet figured, was 

 found by us at the Tortugas. The youngest Tiaropsis described by A. Agassiz * 

 has a deeper bell and more tentacles, but in other respects seems the same. 



Halicalyx tenuis, gen. et sp. nov. 



Plate VII. Fig. 15. 



In January, 1878, A. Agassiz found at Key West a hydroid medusa with 

 the following characteristics. 



Bell low, hemispherical, with thick walls and smooth surface. Apex of the 

 bell destitute of protuberance. The chyniiferous tubes are four in number, and 

 from along their course in the bell hang dendritic ovaries. Through all the 

 windings of the sexual glands there runs a bright crimson stripe, which has 

 the appearance of being jointed. 



The tentacles are twelve in number, and are carried elevated or stiffly 

 extended at right angles to the axis of the bell. They are thickly ribbed 

 along their whole length with lasso-cells, and enlarged at the extremity into 

 a knob. At the base of each tentacle there is an otocyst containing a single 

 otolith. 



The proboscis is short, extending barely to the bell opening, and is without 

 peduncle. The mouth is rectangular, and with short lips, which are sometimes 

 turned backwards and reversed over the outer walls of the stomach. 



Aglaura vitrea, sp. nov. 



Plate VII. Fig. 10. 



A new Aglaura w^as found by us at the Tortugas. The shape of the bell re- 

 sembles that of Trachynema, with which the medusa is easily confounded. 



* North American Acalephffi, pp. 69, 70 ; lUust. Cat. Mns. Comp. Zool., II. ; 

 Proc. Bost. Soc. Nat. Hist., IX. p. 93. See also Morch, Beskriv. af Greenland; 

 and Agassiz, op. cit.; also Mem. Am. Acad., IV. p. 289. 



