TIAROPSIS. 



69 



TIAROPSIS Agass. 



Tiaropsis Agass. Mem. \m. Aoad., IV. p. 2S9. 1849. 

 Tiaroj)sis Agass. Cont. Nat. Uist. U. S., IV. p. 355. 18C2. 



Tiaropsis diademata Agass. 



Titirojisis (Uadumala Agass. Mom. Am. Acad., IV. p. 289, PI. C. 



Tiaropsis diademata Agass. Cont. Nat. Hist. U. S., III. p. 354, PI. 31, Figs. 9 - 15 ; IV. pp. 308 



-311, Figs. 45-48. 1862. 

 Tiaropsis diademata A. Agass. Proe. Bost. Soc. Nat. Hist., IX. p. 93, Fig. 10. 

 Tiaropsii diademata MbucH. ; in Beskriv. af Groeiiland. 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 pei'iod (Fig. 91), spaA\Tis 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 Medusas (Fig. 92), which are fully described in Pro- 



Fig. 91. 



Fig. 93. 



fessor Agassiz's Contribution.^, 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 mai'ginal tentacles of Ilydroids. 



The Thaiimantias Patterson'u 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 lie 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 t<)rty tentacles, c, eye-speck ; f, digestive cavity ; g, chy- 

 miferous tul)e; e, ])rimary tentacles; a, middle teulacle ; i, third set of tentacles in paire; «, fourth 

 aTid fifth sets of pail's of tentacles. 



