150 THE MEDUSAE. 



The series in the present collection is certainly very distinct from 

 P. ladea, but closely related to P. loiigigona and P. mitarctic. From the former, 

 however, it can be distinguished by the much smaller number of tentacles, 

 and from the latter by the shape of the tentacular bulbs. 



Ptychogena erythrogonon, sp. nov. 

 Plate 5, Fig. 1; Plate 38, Figs 8, 9; Plate 39, Figs. 1-7. 



Station 4646 ; 300 fathoms to surface ; 1 good specimen. 



Station 4650 ; 300 fathoms to surface ; 1 small specimen, fair condition. 



Station 4653 ; trawl from 336 fathoms; 3 specimens, somewhat battered. 



Station 4654 ; trawl from 1,036 fathoms ; 3 fragmentary specimens. 



Station 4655 ; 300 fathoms to surface ; 1 large specimen, good condition. 



Station 4661; 300 fathoms to surface; 1 immature specimen, excellent 

 condition. 



Station 4666 ; trawl from 2,600 fathoms ; 1 specimen, fragmentary. 



Station 4671; 300 fathoms to surface; 1 good specimen. Type. 



Station 4675 ; 300 fathoms to surface ; 1 fair specimen. 

 The series is particularly interesting in containing several successive stages 

 in the development of the gonads. Several of the specimens are in excellent 

 condition, and even the fragmentary ones allow most of the details of struc- 

 ture to be made out. 



The form of the bell is characteristic, its gelatinous substance being so 

 thick, and the umbrella cavity so shallow, that the Medusa is almost globular 

 (PI. 39, fig. 1). This character is probably of specific significance, for it is very 

 constant in the series (both in the fresh condition and after preservation), 

 while the three other members of the genus are of more moderate outline. 

 The largest specimen is 38 mm. in diameter by about 25 mm. high. 



Tentacles. — The number of tentacles is much smaller than in either P. 

 ladea or P. longigona. In the only specimen in which the entire margin was 

 preserved, 30 mm. in diameter. Station 4671 in the above table, there were 

 forty-three ; the numbers in each quadrant, counting the tentacles opposite 

 the canals, being twelve, ten, ten, and eleven. In larger specimens the num- 

 ber is greater, the largest number counted in a single quadrant being sixteen, 

 in a specimen 36 mm. in diameter. In the smallest individual, 18 mm. in 

 diameter, there are about twenty-four tentacles in all; and in one slightly 

 larger (24 mm.), but still without any trace of gonads, about twenty-two. In 



