34- 



BULLETIN OF THE BUREAU OF FISHERIES. 



Head short, broad, flattened, averaging about the same width as the mantle. Eyes large and in 

 all but the largest specimens prominently protruding; lid openings with a small sinus in front. 



Arms very short and stout; second and third pairs longest, ventrals shortest, a condition especially 

 apparent in the more minute specimens; lateral arms (especially the third pair) outwardly keeled, but 

 true umbrella wanting. Suckers minute, spherical, in two series. 



Tentacles but little longer than the arms, but their appearance very variable. In the smallest 

 specimen seen (mantle length of 5 mm.) they are slender, fused along their inner faces for the greater 

 portion of their length, but free at the extreme base and at the extremities, which bear a few suckers 

 (3 to 4 each), one of the latter being so conspicuously larger than the remainder as to be barely visible 

 to the unaided eye. In slightly larger specimens (mantle length of 6.5 to 7 mm.) the tentacles are more 

 completely separated but are yet fused for a short diatance near the base of the small recurved pointed 

 club (this is the condition typical of Hoyle's R. chimi), and minute swellings, the rudiments of future 

 suckers, are now visible on the club distal to the large sucker and group of smaller ones mentioned above. 

 Soon after this (mantle length of 9 mm.) the tentacles become entirely free of one another, though still 

 bent strongly inward and with the tips still recurved. Further development is now rapid and the largest 

 specimens show four longitudinal series of extremely minute suckers, those of the two outer rows much 

 smaller than the central ones and already extending down onto the short robust stalk. The four carpal 

 suckers are still separately distinguishable, but are now no larger than the median ones farther distad. 



Color in alcohol a pale brownish buff, the chromatophores brown. The latter show a very constant 

 disposition, forming (1) a broad transverse girdle around the middle of the body, shading paler at its 

 anterior and posterior margins, and (2) an irregular dotting over the dorsal surface of the head, with a 

 tendency to concentrate into two dark roundish spots, one over either eye. 



Measurements op Rhyncoteuthion a. 



Specimens of Rhyncoteuthion a Examined. 



Remarks. — This is a very interesting series and very beautifully shows the ontogenetic transition 

 from the small larva with proboscidiform tentacles similar to that originally figured by Chun to the 

 normal juvenile stage with free tentacles. Originally fused throughout practically their entire length, 

 these organs begin to separate at the base as growth ensties, and then gradually split apart, the carpal 

 region of the clubs marking the point of most persistent adhesion. Microscopical preparations show 

 that the integument is truly continuous at the area of junction and that therefore the union is not merely 

 a mechanical one. 



