16 



EINAR LEA. 



[REP. OP THE "MICHAEL SARS" NORTH 



The head has become a little deformed since capture, 

 but we can see that it resembled the head of L. Syna- 

 phobranchi pinnati very much. Fig. 10 shows the head 

 in its supposed original form, provided with a typical 

 telescopical eye. The snout, quite short but pointed, 

 projects in front of the lower jaw. The jaws are furnished 

 with rather small teeth, the number in each half of the 

 upper jaw being 1-1-13, and in each half of the 

 lower jaw 1 — 6 -\- 10. They are all directed obliquely 

 outwards, the posterior being smaller. The lower jaw 

 lacks the sharp angle characteristic of many other lepto- 

 cephalids. 



The nostrils are separated, and both take the form 

 of pores. The anterior one is situated quite near the 

 point of the snout, and the posterior one about half-way 

 between the anterior one and the foremost margin of 

 the eye. 



4. Leptocephalus Cyematis atri. 



At Stat. 51 one specimen, and at Stat. 56 three 

 specimens were caught, all at a depth of 150 metres, which 

 proved to be the larvae of Cyema atrum. Fig. 5 on pi. 



Fig. 11. Head of larval Cyema atrum. 10 /i. 



II. is a reproduction from a photograph of one of these 

 larvae, and we see that the form is' very peculiar, of shape 

 as an elm leaf the height of body being about half the 

 total length. The alimentary canal with its marked cur- 

 ves adds to the characteristic appearance of this species. 

 The various specimens differ very little in regard to 

 appearance and degree of development. Half of the 

 posterior curve on the alimentary canal is absent in the 



individual from Stat. 51, otherwise the differences consist 

 only in variations in the number and size of the pigment 

 spots on the muscle-segments (see fig. 5, pi. II). In this 

 respect there are also variations between the right and 

 left sides of the same animal. 



The muscle-segments form a very obtuse angle at the 

 lateral line, while they entirely lack the dorsal and ventral 

 angles' usually found in other Leptocephali and fishes 

 generally. 



The head exhibits a very characteristic appearance 

 (see fig. 11), with its eyes in the acute angle formed 

 between the upper contour of the snout and the preci- 

 pitously ascending dorsal margin of the body. The angle 

 between the lower contour of the lower jaw and the ven- 

 tral margin of the body is also acute, approaching 90°. 

 The snout is pointed and long in proportion to the length 

 of the head. There are many teeth, half of upper jaw 

 containing about 20, and half of lower jaw about 16, but 

 they are small, the posterior ones being smaller than the 

 anterior ones, and they are directed obliquely forwards. 



The nostrils not being separated (fig. 11) and the 

 absence of rays in all the fins prove that the four larvae 

 have not yet attained their full development. Only in 

 the pectoral fin can indications of the first traces of rays 

 be seen but they are so indistinct that they cannot be 

 counted with certainty. The interspinous elements, how- 

 ever, are well developed in the vertical fins. In the anal 

 fin we find the first directly behind the anus, and the 

 foremost interspinous element of the dorsal fin of every 

 individual is distinctly developed, and placed at relatively 

 the same distance from the point of the snout. The 

 number of the interspinous elements may thus be used 

 for the following comparison between three of the larvae 

 in question and Cyema atrum, the fourth larva being 

 unfortunately damaged:— 





Larvae 



Cyema 

 atrum 



No. 1 



No. 2 



No. 4 



Interspinous elements in the dorsal fin 

 » . anal „ 



84 

 75 



83 



77 



84 

 75 



86 

 75 



In this particular the larvae accord with the adult 

 Cyema atrum, as is also the case when we compare the 

 number of segments or vertebrae (table p. 17). 



We see that the number of segments in the larvae 

 corresponds well with the number of vertebrae in the 

 adult Cyema atrum, and this is a character of greater 

 value in this species than in any other species of Apodes. 

 For such a small number of segments (vertebrae) does 

 not occur, as far as I am aware, in any other species of 



