lo University of Michigan 



iy2 to 240 (six accurate counts; average 208) ; in the preanal 



fin, only 17 to 24 (average of eleven counts, 21). Highest 



dorsal ray-chambers three to five times as high as long in each 



individual ; dorsal fin about one-sixth as deep as body. Anus 



located well behind middle of lower lobe of caudal fin ; origin 



of this caudal lobe about as near tip of tail as atriopore. Pre- 



atrioporal length, 2.3 to 3.2 (usually about 2.7) times the post- 



atrioporal length. Myotome formula: 34 to 36-!- 12 to 14+6 



to 9=54 to 57 (nine specimens counted). Gonad pouches 22 



to 28 (average of forty counts, 24.6). Maximum length, 



5-35 cm. 



10. Branchiostoma platae Hubbs, new species'' 

 Branchiostoma, sp. Giinther (1884). 

 Branchiostoma lanccoJatuin caribaeuin Lahille (1915). 



Type-material: — Holotype, Cat. No. 85498, U. S. National 

 Museum, collected by the Steamer Albatross at Station 2765, 

 ofif the mouth of Rio de la Plata, South America (lat. 36° 43' 

 S., long. 56° 23' W.) ; depth, 10.5 fathoms; surface temper- 

 ature, 69'' F. ; bottom, sand and broken shells. Eight para« 

 types were also secured by the Albatross : five at the type- 

 station, and three at the adjacent station 2764: lat. 36^ 42' S., 

 long. 56° 23' W. ; surface temperature. 68^ F. ; depth, 11.5 

 fathoms ; bottom, sand and broken shells. 



Diagnosis: — Branchiostoma platae is clearly distinguished 

 from all other species of the genus by the following set of 

 characters: Dorsal ray-chambers, 283 to 327 (average of five 

 counts, 302) ; preanal ray-chambers, 22 to 28 (average of five, 

 26). Higher dorsal chambers four to eight times as high as 

 long in each specimen ; dorsal fin nearly one-fourth as high 

 as body. Anus located far behind middle of lower caudal 

 lobe; caudal fin reduced in size, the base of the upper lobe 



3 Permission to describe this form has been granted by the United 

 States Commissioner of Fisheries. 



