72 DISCOVERY REPORTS 



In most of the specimens the marginal lappets are of equal width and the tentacles of equal size, 

 but occasionally two neighbouring lappets are narrow, indicating that they have newly arisen by the 

 longitudinal division of one of normal width, and the tentacle between them is smaller than the 

 others. The smallest specimen observed (St. 718) is only 10 mm. in diameter; it has 17 tentacles, 

 but evidently this number had recently been attained, since several of the tentacles are much smaller 

 than the others; in one specimen (St. 100), 16 mm. wide with 17 tentacles, several of the lappets are 

 broad with a median incurvation carrying a very small tentacle resembling Bigelow's (1909) fig. 4 

 on PI. 20. An abnormal development has taken place in a specimen, 28 mm. wide (St. 100); its total 

 number of tentacles cannot be stated, but has exceeded 18; most of the tentacles are of equal size and 

 equally spaced, but in one part of the circumference 8 tentacles of very different sizes are placed 

 more or less closely together separated by narrow lappets. 



Among 17 specimens observed, the tentacles could be counted in 13 with the following results: 



No. of 



These figures show that as a rule the specimens attain their final number of tentacles and lappets 

 at an early stage, but occasionally an additional number is developed during further growth of the 



individual. 



I have been able to examine the specimen collected in the central part of the Atlantic by ' Mercator ' 

 and considered by Ranson (1949, p. 135) to belong to Pegantha cyanogramma (Q. & G.). It was 

 kindly sent to me by Dr E. Leloup of Brussels. It is a well-preserved and typical specimen of Pegantha 

 laevis. The diameter is 22 mm., the height 8 mm., the shape is flattened and the jelly fairly rigid. It 

 has 18 tentacles. The gonads are in an advanced stage of development, very prominent and irregularly 

 lobed as in Bigelow (1909, PI. 20, fig. 5). Each marginal lappet has 5 short otoporpae. The lappets 

 are bent strongly inwards and accordingly much contracted transversally; the peripheral canals are 

 extraordinarily broad, their lateral portions frequently considerably broader than the space between 

 them. The radiating folds in the ventral wall of the stomach, described by Ranson, are distinct, but 

 not so regularly arranged as one would expect from Ranson's description. Similar foldings may 

 occasionally appear in the stomach wall of other species. The specimen is entirely different from those 

 identified by Vanhoffen (1908) as Polyxenia cyanogramma, and which undoubtedly belonged to 

 P. triloba. 



Distribution. Bigelow found this species in the tropical East Pacific, partly off the coast of Peru, 

 partly farther west in about 14° S, 115° W, and near the Hawaiian Islands. In the Atlantic it was 

 taken north of the Cape Verde Islands by the Atlantide Expedition (Kramp 1955), and we may now 

 add the locality where the specimen described above was taken by the Belgian vessel 'Mercator'. 

 The Discovery collections show that it is widely distributed in the tropical and southern parts of the 

 Atlantic and in the western part of the Indian Ocean. 



