174 ME. E. T. BEOWNE — BISCATAN PLANKTON : 



the name Hhopalonema coeruleum to the Biscayan specimens, for they come nearer to 

 this sj^ecies as described and figured by Haeckel than to any other species. 



Maas (1905) has described and figured a Rhopalonema which was taken in deep water 

 (500 to 1350 f ms.) by the ' Siboga ' Expedition in the East Indies, under the name of 

 RhoiMlonema cce nil euni, and also states that it is identicsd with Shojyalotietna fuuerarium 

 described by Vanhoffen from the ' Valdivia ' collection. The figures given by Vanhofien 

 and by Maas do not show the top-knot on the umbrella, which is always present in my 

 specimens. Their figures also show longer gonads, which come near the margin of the 

 umbrella. They find four sense-organs in each octant. Their specimens are of larger 

 dimensions than those from the Bay of Biscay. 



HoMCEONEMA PLATXGONON, Maas, 1893. 



Homceonema jjlatygonon, Maas, 1893, p. 15, Taf. 1 ; Browne, 1903, p. 21, pi. .2. 



There are four specimens ; one of them I identified as Homoeonema platygonon, but 

 about the other three 1 was uncertain. They appeared to me to belong to this species, 

 but showed characters of the genus Haliscera. Under these circumstances 1 considered 

 it advi.sable to consult Prof. Maas and let him see the specimens ; he informed me by 

 letter that all the specimens belonged to one species, namelj^, Homceonema platijgonon. 

 As Prof. Maas intends revising the species of the genera Homoeonema and Haliscera, 

 I am glad that these specimens were sent to him. 



Notes on the specimens : — 



(«) This specimen resembles very closely that shown in Maas's figure, but it is at an 

 earlier stage of development. The umbrella is hemispherical, nearly 2 mm. in 

 width and 1 mm. in heiglit. The velum is about OS mm. in width. The stomach 

 is circular, about 0'75 mm. in diameter. There are seven radial canals, instead of 

 eight, which is the normal number. The gonads are just beginning to appear 

 upon the radial canals, adjacent to the stomach. About 5 to 6 tentacle-stumps 

 in each octant. Four sense-organs. 



{b) This specimen is not in very good condition. The umbrella is about 3 mm. in height ; 

 it has a conspicuous cone-shaped mass of jelly, which is quite half the length of the 

 umbrella, above the flat top of the stomach. The cells of the radial canals are 

 in a macerated condition, and I cannot distinguish the generative cells with 

 certainty. The gonads may be regarded as quite immature, 



(/•) The umbrella is a little broader than high, with a rounded summit, and moderately 

 thick. The velum is very broad, exceeding 1 mm. in width. The stomach is 

 circular, 2 mm. in diameter, with a flat top. The moutli is circular, and is 

 expanded nearly to the i^eriphery of the stomach. Eight radial canals. The 

 gonads are upon the radial canals, adjacent to the stomach. In this specimen, 

 M'hich is a female, each ovary is a semicircular swelling containing a few large 

 ova. Erom five of the radial canals the gonads have disappeared, and from the 

 appearance of the canals the ova have evidently been shed. About 10 to 12 



