SEMAEOSTOME^ — DACTYLOMETRA. 



585 



Dactylometra quinquecirrha L. Agassiz. 



Plates 62 to 64A. 



Pelagia quinquecirrha, Desor, E., 1848, Proc. Boston Soc. Nat. Hist., vol. 3, p. 76. 



Dactylometra quinquecirrha, Agassiz, L., 1862, Cont. Nat. Hist. U. S., vol. 4, pp. 125, 166. — Agassiz, A., 1865, North Amer. 

 Acal., p. 48, fig. 69. — Haeckel, 1880, Syst. der Medusen, p. 518. — Fewkes, 1882, Bull. Mus. Comp. Zool. at Harvard 

 College, vol. 9, No. 8, p. 293, plate i, figs. 25-28, 38, 39. — Bigelow, 1890, Johns Hopkins Univ. Circulars, vol. 9, No. 80, 

 p. 65.— Agassiz, A., and Mayer, 1898, Bull. Mus. Comp. Zool. at Harvard College, vol. 32, p. i, plates i-ii, 33 figs. — 

 Hargitt, 1904, Bull. U. S. Bureau of Fisheries, vol. 24, p. 69, plate 7, fig. 2. — Hargitt, 1905, Journal Exper. Zool., vol. 2, 

 p, ^75 (variations).^VANHOKFEN, i<)o6, Nordisches Plankton, Nr. 11, p, 50, fign. 13-14. 



Bathyluca Solaris (damaged and regenerating specimen?), Mayer, 1900, Bull. Mus. Comp. Zool. at Harvard College, vol. 37, 

 p. 2, plate I, 



Chrysaorcy Bigelow, R. P., i88o, Johns Hopkins Univ. Circulars, vol. 9, No. 8, p. 66 (brackish-water variety from Chesapeake 

 Bay). 



Adult medusa. — Bell nearly hemispherical, 170 to 190 mm. in diameter. Numerous 

 small, wart-like clusters ot nematocysts thickly scattered over the exumbrella, especially 

 abundant at aboral apex where they appear as little hemispherical projections above the 

 general surface; near the margin they are elongate in shape, while at the margin itself they 



Figs. 370. — Dactylometra lactea from Havana, Cuba; after Agassiz and Mayer in Bull. Mus. of Comp. Zool. 



A, side view; B, oral view. 



are again hemispherical as at the apex. 8 marginal sense-organs, 40 tentacles, and 48 marginal 

 lappets. The marginal sense-organs are set within niches between the lappets, 4 being per- 

 radial in position and 4 interradial; these niches are protected above by a small web between 

 the lappets. A ciliated, pit-like depression extends downward from the surface of the ex- 

 umbrella immediately above each sense-organ. The sensory-club projects slightly down- 

 ward and contains a distal, entodermal mass of crystalline concretions but no ocellus. The 

 entodermal core of the sense-club is hollow and its lumen is connected with the general 

 gastrovascular space of the medusa. 



There are 5 tentacles between each successive pair of sense-organs. 3 of these tentacles, 

 the primary and secondary, arise from the clefts between the lappets, but the other 2 (tertiary) 

 are generally found to spring from the under or subunibrella side of the ocular lappets; for 

 even in very large medusae the ocular lappets exhibit but a slight notch adjacent to the ter- 



