SYSTEMATIC REPORT 41 



Remarks. Characters used by M. Sars (1857) to define Lophogaster typicus have proved to be 

 variable and unreliable. Fage (1942, pp. 7-39), in a survey of all the known material of the species, 

 divided it into four distinct species: (1) typicus (for the forms from the northern hemisphere); (2) 

 challengeri (for specimens collected by ' Challenger ' in South African waters and described by 

 G. O. Sars as typicus — the new specific name emphasizes the fact that these specimens are the true 

 types of challengeri); (3) pacificus and (4) hazvaiiensis. 



Fage separated his four species on the following four salient characters of the carapace: (1) the 

 tuberculation of the integument, (2) the presence or absence of a post-orbital spine, (3) the shape of 

 the profile (in lateral view) of the dorsal margin of the free postero-lateral regions or ' wings ', and (4) the 

 size and angle of the postero-lateral spine. He showed, moreover, that these characters were corre- 

 lated with geographical distribution and conditions of the habitat. 



At first sight it may seem that these characters are too trivial to warrant the separation of challengeri 

 from typicus, but examination side by side of specimens from the northern and southern hemispheres 

 leaves no doubt that they do represent two different species and I have no hesitation in accepting 

 challengeri as valid. 



Fig. 2. Lophogaster challengeri Fage. A, anterior end in dorsal view, x 10; B, lateral view of postero-lateral region of carapace 

 ('wing'); C, telson and right uropod in dorsal view, x 10; D, distal end of telson (enlarged), x 19. Iww*.. Sh«-. 



9 



The integument of the carapace, especially in the mid-dorsal area, is covered with more or less 

 well-developed tubercles in both typicus and challengeri. This condition is much more pronounced in 

 juveniles and as growth proceeds the tubercles tend to disappear. In the Discovery specimens these 

 tubercles are comparatively few in number and very large. The animals are all small and very immature 

 and since neither Sars nor Fage mentioned the tuberculation of the integument of the carapace in 

 their larger specimens of challengeri, I assume that, as in typicus, the tubercles become less pronounced 

 with growth. 



In small juveniles of both species the margin of the carapace bordering the eye is fringed with 

 a close row of fine teeth which disappear completely with growth. In L. typicus this pectination can 

 still be seen in animals of 12 mm. in length but in L. challengeri it disappears much earlier. At 

 station 277 (haul 1) all the specimens of less than 5 mm. in length had marked pectination but in those 

 of 5-5-5 mm. only very faint traces of it remained. I could not see any sign of the pectination of the 

 margins of the epimeral plates such as occurs in juveniles of L. typicus. 



G. O. Sars (18856, p. 14) neither mentioned nor figured a post-orbital spine in his Challenger 

 specimens, although M. Sars made a special point of it in his original description of L. typicus. 

 Examination of the Challenger specimens confirms that they have no such spine and I am unable to 

 find one in the Discovery specimens, which I here refer to challengeri. In all the European specimens 



