EISEN 



are separated by epithelial cells which greatly resemble those of P. 

 sonorce. Below the epithelial cells are seen broad interstitial cells 

 with large meshes of cytoplasm. It is to be noted that F. fuchsi and 

 F. sonorce also resemble each other in the form of the spermathecae 

 and in the absence of spermathecal diverticles. These two species 

 differ from all others so far examined by me, by the long and flat epi- 

 thelial cells of the intestine. In F. sonorce the chylus cells are not as 

 high. 



Muscular layer. The outer muscular layer of the body- wall is 

 quite characteristic. It rises at certain short intervals into the epithe- 

 lium, almost completely separating these cells. In cross-section these 

 strands are triangular, with the apex pointing toward the cuticle. 



FRIDERICIA SONOR^: sp. nov. 

 pi. xvi, figs. 1-3 ; text-fig. 75. 



Definition. Length 12 mm., width .5 mm. Somites about 40. 

 Setae in bunches, anteriorly of 6, posteriorly of 5, 4 and 3. The 

 outer ones are much larger than the inner ones. Prostomium small 

 and pointed. Clitellum XII and XIII. Sexual papillae small. Brain 

 ovoid. Dorsal vessel rises posterior to clitellum. Intestine with 

 chylus cells in the two or three somites next posterior to clitellum. 

 Spermathecae with a large globular ampulla which does not connect with 

 the intestine. Penial bulb small, with a single row of glands opening 



into the lower part 

 of the sperm-duct, 

 which latter is not 

 dilated. Lympho- 

 cytes of two kinds, 

 the large ones 

 small, oval, of a 

 diameter equaling 

 that of two or three 

 muscular strands. 

 The microcytes are 

 from one diameter 

 to half the diameter of a muscular strand. Color pale yellowish-white 

 without pigment. Nephridia with a very large anteseptal. 



Locality. San Miguel de Horcasitas, Sonora, Mexico, in soft 

 banks of irrigation ditches, May, 1893. Four small specimens, all 

 containing sand, causing the loss of many sections. The salivary 



FIG. 75. Fridericia sonorce. 



