240 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



1. Two pairs of lateral fins, the posterior pair much larger and confined entirely 

 to tail-segment, beginning directly behind seminal receptacle. Anterior 

 pair extends throughout posterior third of body, beginning directly in 

 front of seminal receptacles. Ventral transverse muscles present only in 

 anterior half of body S. schizoptera . 



KEY TO SPECIES OF EUKROHNIA. 



1. Anterior two-thirds of lateral fins rayless. Posterior extremity of fins less 

 than half-way from tail-septum to seminal vesicles. Width of body less 

 than 8 per cent of total length of animal. Seizing jaws delicate; some- 

 times serrated 2 



1. Lateral fins delicately rayed throughout. Posterior extremity of fins at 



least three-fourths way from tail-septum to seminal vesicles. Width of 

 body exceeds 12 per cent of total length of animal. Seizing jaws massive; 

 not serrated - ^ E. richardi. 



2. Eyes without pigment. Seizing jaws 8-10, gently curved throughout. 



Points sickle-shaped E. hamata. 



2 Eye with pigment. Seizing jaws 11-13, sharply curved in anterior quarter. 



Point slightly curved toward edge of jaw, but not sickle-shaped E.fowleri. 



SPECIES OBTAINED DURING THE PHILIPPINE EXPEDITION. 

 Genus SAGITTA Quoy and Gaimard. 



SAGITTA PHILIPPINI, new species. 



Plate 34, figs. 1-4. 



General appearance. To the naked eye S. pJiilippini, when placed 

 in formalin upon a white background, appears white in color, scarcely 

 distinguishable from the background. Its head and tail, and in less 

 degree its ovaries, assume a brownish-yellow color in marked con- 

 trast to the body proper. On a black background the head, ventral 

 ganglion, ovaries, tail, seminal vesicles, and to a less extent the 

 intestine appear much more opaque than the body, which resembles 

 ground glass. The lateral fins and tail fin are so transparent as to be 

 invisible to the naked eye. In degree of opacity S. philippini 

 resembles 8. decipiens more than any other species, although it is 

 perhaps less transparent. 



Characters. Collarette absent. Neck conspicuous. Lateral fields 

 prominent. Body flabby, not retaining its form well; widest behind 

 center, tapering gradually forward toward head and backward 

 toward tail. No constriction at tail-septum. Ovaries, even when 

 immature (pi. 34, fig. 1), extend beyond posterior end of anterior fin. 

 Corona ciliata not observed. 



Anterior fins (pi. 34, fig. 1) rayless throughout anterior half of fin. 

 They are longer and narrower than posterior fins, and extend ante- 

 riorly beyond posterior end of ventral ganglion. Form triangular, 

 the position of greatest width being in the caudal quarter of fin. 

 Interval from anterior to posterior fins slightly greater than maximum 

 width of body. 



Posterior fins do not extend caudally to seminal vesicles. More 

 than 50 per cent of fin in front of tail-septum. Form triangular, 

 the position of greatest width being at or just behind tail-septum. 



