THE CH.ETOGXATHA. 65 



The occvirrences at and 25 fathoms AAere so few that no indication of any reaction 

 to time of day, light, or rain coukl lie expected, even if snch reaction existed. At 

 50 fathoms and down to 100 the specimens are so closely massed that we may regard 

 the captnres at 25 and as stragglers from the main hody, just as those hetween 200 and 

 100 fathoms. 



Sagitta mackocephala, sp. n. (PL 5. figs. 16-21.) 



This species, coming only from considerahle depths, presented but few specimens in 

 sufficiently good condition for accurate description. The following points, however, 

 will serve for diagnosis until l)etter specimens are recorded by other observers. 



Characters. — Head very large, forming when fully expanded a truncated triangle. 

 Neck narrow and without a " collarette." Body slender, firm, but much thicker in the 

 middle than anteriorly ; lateral helds not large. Tail-segment about one-third or more 

 of the total length ; tip of tail generally bluntly conical. 



Anterior fins small and (?) rounded ; j^osterior lins larger, rounded rather than 

 triangular, al)out equally divided between trunk and tail; tail-tin often pointed 

 posteriorly. 



Jaws curved throughout their whole length, sharply so in the distal fourth. Teeth 

 very dark in colour, borne on an unusually stout bar. Teeth of the anterior row lone 

 and slender, slightly curved inwards to the middle line, their bases touching, but in 

 complete expansion of the head they project radially outwards as a half-circlet. Teeth 

 of the posterior row very numerous, closely set, long, and slender; in complete expansion 

 of the head they form a curve which goes completely from the dorsal to the ventral 

 surface, so that the dorsalmost point outwards, the ventral most inwards. 



Corona ciliata not observed. Vestibular ridge covered v.ith a thick cuticle; it extends 

 externally for the Avhole length of the row of posterior teeth, internally somewhat 

 further, and carries irregitlar ])romiuences fewer in number than the teeth. 



Body sometimes salmon-pink, sometimes colourless. As tlie generative organs were 

 quite rudimentary in even the largest specimens, it is probable that only immature 

 specimens were captured. 



The great size of the head and the large number of teeth, compared with the size of the 

 body, mark this species off from all others hitherto recorded. 



The f olloAving table * covers all measurable specimens captured ; where the per- 

 centage of the tail is not given, the total length must be taken as only an approximation. 



DistrihutioH. — The vertical distribution of this species is conspicuously show n in the 

 table p. 84, and the diagram PL 7. It occurred in 63 per cent, of the 19 hauls which 

 closed at or below 100 fathoms ; the only otiier certain captures were in deep hauls open 

 from 1250 fathoms to the surface (27 «, 27 «')• Six very small specimens from 32 ;, 

 85 k, and 36 I may be larvae of this species {nmcroeephala). It failed entirely in the 



* The six specimens below the transverse lino in the table include all the specimens from 32 Z, 35/.-, 3(H that is 



all the shallower occurrences. 1 think that they are larval macrocejjhitla, but they are very small and the number 

 of posterior teeth drops rather suddenly. They are included in the curve macrocej>hula on Pi. 7. 



11* 



