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PROCEEDINGS OF THE 



[April, 1857. 



downwards, the cavity within elongating with them, fig. 6, a. 

 At first there appears to be but one cavity; a slight constriction 

 appears on the elongating tentaculum just below the margin, and 

 in the next stage known to me, fig 5., there are two sinuses con- 

 nected by a canal through the tentacular shaft, in the engraving 

 represented by a median line passing from the dark central core 

 of the ocellary bulb to the hollow enlargement c, at the extremity 

 of the tentaculum. The young Medusa at this stage is free, with 

 but two tentacula, though with four marginal bulbs. Each ten- 

 taculum has one or two patches of thread-cells, besides the en- 

 largement at the end. The bell-wall is still very thin ; the digest- 

 ive trunk large, conical and pointed below; the mouth not yet 

 perforate. In a day or two, from the remaining two bulbs, tentac- 

 ula begin to sprout, which soon obtain a complete resemblance 

 to the other two, though for some time after they are perceptibly 

 inferior in size, thus giving a sort of bilateral symmetry to the 

 animal. It should be remarked that the cavity or sinus in the 

 terminal bulb of the tentaculum is lined by colored cells similar 

 to those which line the cavity of the ocellary bulb, and in my 

 opinion, also, to those which line the digestive cavity. 



This development shows that we should be careful in founding 

 new genera upon a difference in the number of tentacula. 



Distribution. Charleston Harbor. 



CORYNITIS AGASSIZII, nov. spec. 

 PI. 9. Ff. 3—8. 



When fully grown, this species is nearly of the size of Turri- 

 topsis nutricula, about .3 in. in height, which was the size 

 of the specimen figured fig. 3 ; that from which fig. 4 was taken 

 having been in contracted condition and smaller. The gen- 

 eral form is mitrate, the outline swelling out as on either side it 

 rises from the tentacular rim, and terminating above in a rather 

 obtuse vertex. The outline is broken by slight protuberances at 

 tolerably regular intervals, which are the bulging clusters of 

 thread-cells, scattered over the whole outer surface. The massive 

 digestive trunk has a little more than its upper third occupied by 

 the digestive cavity and the sexual organs. The remainder is pro- 

 longed in the form of a tube terminated at the mouth by several 

 (3? or 4?) indistinct lobes. This tube is capable of extending it- 

 self beyond the vail or of almost confounding itself with the upper 

 and more stationary portion by contraction. The large ova, of 



