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PROCEEDINGS OF THE NATIONAL MUSEUM 



10th legless^ 

 body -ring 



Figure 4. — a, Lateral view of portions of the abdomen and telson of a male of Apus longicau- 

 datus LeConte (U. S. N.M. No. 11604) showing a left-handed spiral of about two and 

 three-quarters rounds, beginning dorsolaterally and evenly tapering at distal end, X 28. 

 Arrangement of muscle bundles indicated on the left side. (Sp, spiral; T, telson.) 

 b. Schematic drawing of the spiral. 



Figure 5. — a, Ventral view of portions of the abdomen and telson of a female of Apus 

 longicaudatus LeConte (U.S.N. M. No. 82034) showing a right-handed spiral of two 

 rounds placed within the series of normal rings and beginning and ending in the mid- 

 ventral line, X 29. {Sp, spiral; T, telson.) b, Schematic drawing of the spiral and the 

 rings immediately anterior and posterior to it. 



