146 PROCEEDINGS OF THE NATIONAL MUSEUM vol. i04 



men was taken in the vicinity of Fort San Geronimo, west end of San 

 Juan Island, Puerto Rico, Mar. 27, 1937. The specimen shattered on 

 an attempt to mount it whole and had to be discarded. 



Genus Enchiridiiini Bock, 1913 

 Enchiridiutn periommatuni Bock, 1913 



Figure 89, c 



Enchiridium periommatum Bock, 1913, p. 287, text figs. 64-66, pi. 5, fig. 6. 



Material: One preserved specimen sent by H. J. Humm. 



Form: Typical of the genus, elongate, with rounded anterior end 

 and bluntly pointed posterior end (fig. 89, c). The specimen was 30 to 

 40 mm. long, alive, when moving, by 10 to 12 mm. wide; on preserva- 

 tion the animal contracted to a length of 23 mm. 



Eyes: There is the usual pair of cerebral clusters, close together; 

 they contain more eyes than as depicted by Bock. The marginal eyes 

 completely encircle the margin, as diagnostic of the genus, and the 

 arrangement is similar throughout the genus, that is, the marginal 

 band is wide around the anterior end but, at about the level of the 

 anterior part of the pharynx, rapidly thins to a single file of eyes that 

 continues along the rest of the margin. 



Color: Bock was unable to give the color of his specimen. Thanks 

 to notes furnished by Dr. Humm, it can be stated that the species is 

 white, dotted with rounded browD spots that are more concentrated 

 in the middorsal region and more scattered towards the margin and 

 posterior end, as shown in figure 89c. It appears that all three species 

 of Enchiridium known from the shores of the American continent have 

 the same color pattern. 



Digestive tract: Identical throughout the famil}^, with long tu- 

 bular pharynx in the anterior region opening by the mouth shortly be- 

 hind the brain and long main intestine giving oft' side branches. 



Copulatory apparatus: Removed from the specimen and sec- 

 tioned and found in good histological condition. As Bock has figured 

 the apparatus, it appears umiecessary to illustrate it here or give a 

 detailed description. The female gonopore is half way between the 

 male gonopore and the sucker as shown in figure 89, c; the male 

 apparatus and gonopore were displaced laterally in the specimen, no 

 doubt as a result of distortion during fixation. The male antrum 

 leans forward more in the specimen than as shown in Bock's figure but 

 otherwise there is good agreement with Bock's figures. The very 



