K.EPOKT ON THE DEEP-SEA MEDUSAE. 103 



and of the Collaspida (AtoJla) on the other. Like Atolla, Nauphanta is a true deep-sea 

 form of high phylogenetic antiquity. 



Nauplianta challengeri, Hseckel (Pis. XXVI. , XXVIL). 



Nauphanta challengeri, Hreckel, 1879, System der Medusen, p. 487, No. 452. 



Umbrella cap-shaped, with a horizontal apical surface, and vertical side- wall, one and a 

 half times as broad as high. Exumbrella with a deep coronal furrow and sixteen deep radial 

 furrows. Umbrella corona with sixteen pedalia (eight smaller rhopalar and eight stronger 

 tentacular) ; sixteen marginal lobes oval, nearly twice as long as broad, with a deeper 

 peronial furrow, about one-fourth as long as the radius of the umbrella. Tentacles 

 cylindrical, pointed, about as long as the radius of the umbrella. Genitalia eight oval, 

 adradial, kidney-shaped swellings, twice as long as broad ; their proximal halves some- 

 what broader than their intervals, their distal halves covered by the coronal muscle. 

 Horizontal diameter, 12 mm. ; vertical diameter, 8 mm. 



Habitat. — The South Atlantic Ocean, not far from the island of Tristan da Cunha. 

 Lat. 32° 24' S., long. 13° 5' W. Depth, 1425 fathoms. Station 335. Both specimens 

 examined (a male and a female) are well preserved, and were taken on 16th March 

 1876. The transverse and longitudinal sections figured are taken from the two halves 

 of the halved female specimen. 



The umbrella (PI. XXVIL fig. 1 ; PI. XXVIII. figs. 12-14) of Nauphanta 

 challengeri has the form of a cap or biretta, and is considerably more vaulted than in 

 most other Discomedusas. Its special conformation, and especially the peculiar 

 sculpture of the exumbrella, reminds us in many respects of the Cubornedusas and 

 Peromedusas, with which the oldest ancestral forms of the Discomedusas are clearly very 

 closely allied. Whilst the upper flattened apical surface appears almost horizontal, 

 the steep, vertical side walls stand almost vertical. The umbrella is constricted 

 between the first or second third of its height by a deep horizontal coronal furrow 

 (" fossa coronalis," ec), and is thereby divided into an upper (central) umbrella disc, 

 and a lower (peripheric) umbrella corona. The umbrella disc (" discus umbrellas "), 

 which is depressed above like a cup in the middle, forms the horizontal cover of the 

 flat discoid basal stomach (gb) ; the umbrella corona (" corona umbrellas ") encloses the 

 corona of the radial pouches, and bears below at the margin the corona of the tentacles, 

 and rhopalia, and the marginal lobes alternating with them. 



The exumbrella (figs. 1, 13) is distinguished by the horizontal coronal furrow (ec), 

 and also by deep, radial, or longitudinal furrows, which, as raPeriphylla (Pis. XIX., XX.), 

 divide the external surface of the umbrella into convex, projecting, gelatinous swellings. 

 We can distinguish on the whole sixteen deep, subradial, longitudinal furrows, and 

 sixteen shallower, alternating with them. The latter traverse nearly the whole 



