NO. 2286. THE NEW COPEPOD FAMILY SPHYRIIDAE— WILSON. 557 



The trunk is more or less enlarged and flattened dorso-ventrally ; it 

 is usually heart-shaped, the apex of the heart joining the neck, but it 

 assumes an elongated club shape in Opimia and Paeon fero.v. The 

 surface is normally smooth and convex, but as a result of the contrac- 

 tion of the internal dorso-ventral muscles it may become pitted when 

 those muscles are universally distributed, or may exhibit a few larger 

 depressed areas, symmetrically arranged, when the muscles are gath- 

 ered in bunches. The wall of the trunk is rather thin and so soft that 

 in some species, such as Paeon fe7'ox, it is easily pressed out of shape. 

 In young females the posterior end has not yet assumed the typical 

 heart shape, but is narrowed into a rounded lobe terminated by large 

 anal laminae (sec fig. 17). xVs growth progresses and the heart shape, 

 with its median sinus and lateral lobes, is assumed the rounded lobe 

 disappears and the anal laminae become flattened together and thick- 

 ened until in the mature adult they form together a small hemispheri- 

 cal knob, nearer the dorsal than the ventral surface. On either side 

 of the laminae and ventral to them is a genital knob, out of which 

 opens the oviduct. 



From the dorsal surface of the genital segment and the anal laminae 

 arise a pair of posterior processes. Tliese may develop into long, 

 smooth, simple cylinders {Opimia., Paeon)., or they may become 

 lobed (Periplexis) , or they may begin to branch and the branches may 

 divide dichotomously until they assume a fancied resemblance to 

 bunches of grapes (grappes de rasins) as in the genus Sphyrion^ or 

 each branch maj'^ grow into a long and narrow cylinder, in Avhich 

 event the whole process is likened to a tuft of hair (faisceau de poils) 

 as in the genus Eehelula. 



Here again, of course, the size and complexity of the final mass will 

 depend largely upon the age of the specimen examined, and will be 

 of practically no value in determining species. 



The egg strings are straight and cylindrical and the eggs inside 

 them are small and multiseriate, but are not arranged definitely in 

 rows as in the Lernaeopodidae. 



The appendages are the same as in the Lernaeidae, namely, two 

 pairs of antennae, a pair of mandibles, tAvo pairs of maxillae and a 

 pair of maxillipeds. But these can onlj^ be seen in young females 

 and males; some or all of them are wanting in the matured female 

 adult. 



The first antennae in the young Sphyrion female (fig. 18) are on 

 the anterior surface of the head, dorsal to the mouth tube, and are 

 minute in size and destitute of setae. The second pair are at the sides 

 of the mouth tube; they have swollen basal joints and are tipped with 

 the rudiments of a chela. The mouth tube is at the center of the an- 

 tero-ventral margin of the head and is directed diagonally forward 

 and downward. It is made up of a distinct labium and labrum, the 



