TIAROPSIS. 



69 



TIAROPSIS Agass. 



Tiaropsis Agass. Mi-in. Am. Acad., IV. p. 289. 1849. 

 Tiaropsis Agass. Cont. Nat. Hist. U. S., IV. p. 355. 1862. 



Tiaropsis diademata Agass. 



Ti(irnj)sis dkulematn .\gass. Mem. Am. Acad., TV. ]). 2X9, PI. G. 



riaropsis illothmata Agass. Cont. Nat. Hist. U. S., HI. p. 354, PI. 31, Fifrs. 9-15; IV. pp. 30H 



-311, Fijrs. 45-48. 1862. 

 Tiaropsis <li,u/('»ial(i A. Agass. Proc. Bost. Soc. Nat. Hist., IX. j). 93, Fi^^. lo. 

 Tiaropsi,'! ilimhmala MoKCii. ; in Beskriv. at' Groenland. 1857. 



This Medusa is one of the earhest visitants of our wharves in the 

 spring. Ill company with Sarsia and Syndictyon, it occurs in <:;reat 

 uuiiil)ers during the spring months ; it attains its full size in a coin- 

 parativcly short period (Fig. 01), spawns during April and May, and 

 after tiiat it is found Init rarely, disap))eariug totally during the sum- 

 mer. Although so common, the Hydroid of this Medusa has not heen 

 observed. Young Medusae (Fig. 92), which are fully described in Pro- 



Fig. 91. 



Fig. 93. 



fessor Airassiz's Contributions, are exceedinijlv numerous. The tentacles 

 develop independently of the eyes, while the latter never increase in 

 number. (See Fig. 93.) For a more detailed description of their mode 

 of growth, see also my paper on the marginal tentacles of Hydroids. 



The Jlimimantias Patter sonll of Greene seems to me, as far as 1 can 

 make out from his description and figures, to belong to the genus Tia- 

 ropsis. There must be some error in his view from above, in which he 

 represents black ocelli at the base of the chymiferous tubes ; I doubt if 



Fig. 91. Tiaropsis diademata, natural size. 



Fig. 92. Young Tiaropsis, having twenty-four tentacles. 



Fig. 93. Young Tiaropsis, having forty tentacles, c, eye-speck ; /, digestive cavity : cj, chy- 

 miferous tube; e, primary tentacles ; a, middle tentacle; b, third set of tentacles in paii-s; a. fourth 

 and fifth sets of pairs of tentacles. 



