556 PROCEEDINGS OP THE AMERICAN ACADEMY. 



and floated upon glass slides. These preparations were ready for study 

 as soon as they were dry. 



The whole surface of the proboscis, except the part which is most 

 anterior in the usual state of eversion (Fig. 1), is covered with conical or 

 thirnble-shaped papillae, which are arranged on the summit of transverse 

 folds (PI. 5, Figs. 32, 33). In general the axes of the papillae are per- 

 pendicular to the surface of the proboscis, or are directed outward and 

 either slightly backward or slightly forward. The rows of papillae are 

 as a rule separated from each other by regular intervals, but sometimes 

 there is an anastomosis (Fig. 32) of the folds from which these organs 

 project. The folds follow one another closely, and there are one or two 

 rows of papillae to each fold. At the posterior part of the everted 

 proboscis the transverse rows are divided into eighteen longitudinal 

 groups (Fig. 33); the interspaces correspond to the position, of the 

 eighteen longitudinal nerves. Otherwise the arrangement and frequency 

 of these organs is the same from the anterior to the posterior end of the 

 jiroboscis, and there is no other evidence of special grouping in any part. 



The papillae are more or less ovoid or conical. On a proboscis about 

 o^- mm. in diameter at the anterior end, they were found to be about 

 80 [jl in height and about 35 /x in diameter at the thickest part. 



The cuticula of the proboscis passes over each papilla, but is here re- 

 duced to about two-thirds the thickness it has elsewhere. The cuticula 

 of the posterior face of each papilla is coarsely corrugated. The 

 ridges are most clearly seen in preparations of removed cuticula (PI. 6, 

 Fig. 34), or in sections stained in Kleinenberg's haematoxylin (PI. 1, 

 Fig. 6 ; PI. 3, Fig. 13). Though varying in number in different 

 papillae, the ridges show considerable regularity of form and arrange- 

 ment, for the outlines produced by them are always rather sharply bent 

 in a region corresponding with the middle of the posterior face of the 

 papillae, so that the surface view of that face shows a series of V-shaped 

 outlines, like the longitudinal section of a nest of funnels, the apices of the 

 V's being directed toward the base of the papilla. Sometimes, however, 

 there is an anastomosis of the folds (PI. 3, Fig. 13). Elders (p. 679) 

 says of this species of Rhynchobolus that the cuticula of the papillae has 

 " fine folds, which, like those of the gills, occur in spiral lines, surround- 

 ing the papilla, or more rarely, standing out as sharply projecting 

 ridges." Concerning the gills he says (p. 676) : " The chitinous cov- 

 ering possesses at fairly regular intervals furrows which pass around 

 the circumference spirally ; their significance probably consists in their 

 laying the gill into definite folds when it collapses and withdraws into 



