NO. 1368. DESCRIPTIONS OF AKULLW.E—WILSOX. 643 



surface pij^ment. which is so dense just in front of tlic side lininclies 

 of the stomach where tlu^se olands are situated, and also in nianv 

 oth(n- places, as to conceal all details of internal structure". The eir- 

 culation is similar to that ch'seribed in other larva' except for the 

 absence of a well-detined peripheral sinus in both the abdomen and 

 the cephalo-thorax. 



Th(> internal cellular lacuna> appear about the same, but the currents 

 are not as well detined, espin-ially those of th(" abdomen. This larval 

 circulation is carried on chiefly by means of certain muscles in the 

 cephalo-thorax and abdomen, similar in both position and function to 

 those already descrilied for niegalopx. The heart lias not yet appeared, 

 and hence those differences which make the adult circulation peculiar 

 can not yet be detected. The transverse dorso-ventral band or curtain 

 at the place occupied later by the posterior wall of the heart is not 

 as well developed as in megalops larvjB, another natural result of the 

 differences in the period of development. 



Furthermore, in view of the immature condition of all the swim- 

 iiiinjj" legs except the first pair, the muscles in the basipods of those 

 appendages can not aid circidation to an}' appreciable extent. In fact, 

 the undeveloped condition of most of the larval organs may well 

 explain the feeble circulation. 



As soon as the heart acquires deffnite form after the lirst moult we 

 should ex))ect to tind the circulation showing the same peculiarities 

 as in the adult. 



The nervous and reprodiactive S3'stems present no peculiarities 

 worthy of special note, but are similar to those already descril)ed in 

 the adult. 



ARGULUS VERSICOLOR Wilson. 



Arffuhis versicolor Wii.sox, Proc. U. S. Nat. Mu8., XXV, ]>. 71(i. 



This is a ver}' clean-looking Argulus and by far the most beautiful 

 of any American species. It can be distinguished from all others at a 

 glance by its brilliant coloration, which is as variegated as that of an 

 old-fashioned patch-work quilt or the traditional Jos(>])h's coat. The 

 ground color is a soft yellow-green, which forms a wide border around 

 the edge of the carapace and extends inward in a series of bands and 

 irregular spots, the former being a deeper green than the margin, 

 while the latter have somewhat of a rusty tinge. One of these bands 

 runs from the marginal border on either side just behind the sucking 

 disks diagonally backward to the base of the central longitudinal ribs. 

 From the center of each diagonal band another narrower one extcMids 

 backward parallel with the edge nearly to the posterior margin of the 

 carapace. These longitudinal bands are joined with the marginal l>or- 

 der at about their center by a short radial l)and. which shows the same 

 rusty tinge as the spots. These latter are found just outside the mi.1<- 



