REPORT ON THE DEEP-SEA MEDUSAE. 7 



Ptychogena pinnulata, Haeckel (PI. II.). 



Pti/choijena pinnulata, Hreckel, 1879, System del Medusen, p. 148, Xo. 150. 



Umbrella depressed, three to four times as broad as high. Stomach quadrangular, very 

 flat and wide, one-third of the diameter of the umbrella, with slightly-raised oral margin, 

 which is prolonged at the corners into four short lobes. Genitalia, four broad, almost 

 circular, pinnated leaves, which occupy the proximal half of the radial canals, at whose 

 conically-enlarged origin they pass into the wall of the stomach, each leaf with twenty to 

 thirty pairs of alternating pinnated branches, which are not divided, and which bear 

 leaf-shaped, deeply-notched reproductive lobes at the lower free margin. Two to three 

 hundred long tentacles with numerous marginal clubs between. Horizontal diameter of 

 the umbrella, 50-60 mm. ; vertical diameter, 20-30 mm. 



Habitat. — North Atlantic Ocean. I was able to investigate several well-preserved 

 specimens in spirit of this North Atlantic species from the Copenhagen Zoological 

 Museum, which had been found by Captain Moberg between Ireland and Iceland (lat. 59° 

 7' N, long. 13° 32' W. from Greenwich). A fragment of a Cannotid, which 1 dis- 

 covered in a jar of the Challenger collection, from Station 50 (May 21, 1873), in the 

 same jar as Pectyllis arctica (dredged near Halifax from a depth of 1250 fathoms, lat. 

 42° 8' N, long. 63° 39' W.), appears identical with these specimens. Although this 

 decomposed fragment hardly included the quadrant of a disc, it was still sufficient to 

 identify it completely with these Copenhagen specimens from which the following descrip- 

 tion and drawing are taken. 



Ptychogena pinnulata shows, on the whole, the same formation of the umbrella as 

 the closely-related Ptychogena lactea (loc. cit.). The umbrella is depressed, projecting 

 somewhat more strongly in the centre. The horizontal breadth at the opening of the um- 

 brella cavity is from two to three times as great as the vertical height. The gelatinous 

 substance of the umbrella is tolerably firm, but thin, and diminishes in thickness rather 

 rapidly from the centre towards the margin ; in the centre its thickness amounts to 

 5 or 6 mm. The exumbrella is smooth, without special distinct characters. 



The umbrella margin is thickly beset with two rows of appendages, an outer row of 

 long tentacles, and an inner row of short marginal clubs (figs. 3, 4). The number of 

 tentacles or marginal filaments amounts to from 200 to 300 ; in one specimen I counted 

 320. There are usually from 70 to 80 upon each quadrant. They lie thickly pressed 

 together. The swollen basis or tentacle bulb is 1/8 mm. long, - 6 mm. broad, and has 

 the form of a half-oval leaf lying in the meridian plane. The abaxial margin is strongly 

 arched, rising gradually from the basis, and then falling off rapidly. The axial margin is 

 straight or sinuated a little concavely. The marginal filament itself is very thin, and in 

 the spirit specimens before me nearly as long as the diameter of the umbrella ; in the 

 living animal probably three or four times as long. The marginal clubs, or tactile clubs 



