TIAROPSIS. 



69 



TIAROPSIS AGASS. 



Tiaropsis AGASS. Mem. Am. Acad., IV. p. 289. 1849. 

 Tiaropsis AGASS. Cont. Nat. Hist. U. S., IV. p. 355. 18G2. 



Tiaropsis diademata AGASS. 



Tiaropxh dlcidi-mnta AGASS. Mom. Am. Acad., IV. p. 289, PI. 6. 



Tiuropxix did< nutta AGASS. Cont. Nat. Hist. U. S., III. p. 354, PI. 31, Figs. 9-15; IV. pp. 308 



-311, Figs. 45-48. 18C2. 



T/C//-O/J.V/.S- diiidcmitta A. AGASS. Proc. Bust. Soc. Nat. Hist., IX. p. 93, Fig. 10. 

 Tiuropsig diademata MORCII. ; in Beskriv. af Groenland. 1857. 



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

 spring. In company with Sarsia and Syndictyon, it occurs in great 

 numbers during the spring months ; it attains its full size in a com- 

 paratively short period (Fig. 91), spawns during April and May, and 

 after that it is found but rarely, disappearing totally during the sum- 

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

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



rig. 91. 



Fiz. 93. 



Fig. 92 



fessor Agassiz's Contributions, are exceedingly 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 Thaumantias Pattersonii of Greene seems to me, as far as I 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 ; g, chy- 

 miferous tube; e, primary tentacles ; a, middle tentacle; b, third set of tentacles in pairs; , fourth 

 and fifth sets of pairs of tentacles. 



