318 J. W. KIEKALDY. 



mediaa fin (as iu Heteropleuron) ; left raetapleur dying out 

 immediately behind the atriopore. 



Infra-rostral fin in direct continuity with both the right and 

 the left metapleura. Atrial chamber extending behind the 

 atriopore as two laterally paired caeca. Prseoral tentacles devoid 

 of sensory papillae. Gustatory groove of Hatschek (on the right 

 side of the roof of the preeoral liood) very deep and pit-like. 



Species unica. — A. Lucayanum, PI. 34, fig. 3. 



AsYMMETEON LucAYANUM, Audrews. ' Johris Hopkins Univ. Studies,' 



1893, p. 213. 



Myotomes, maximum number 69, minimum number 63, 

 usual number 65 — 66. 



Myotome formula 48, 8, 12 ; 44, 9, 13 ; 45, 10, 14; 46, 10, 

 12 ; usual formula 44, 9, 13. 



Dorsal fin of moderate height (one seventh of length from 

 crest of fin to edge of metapleur at mid-body). Rostral fin 

 very slightly developed, either above or below the notochordal 

 rostrum, which, however, is of unusually great length. Ventral 

 fin devoid of fin-ray chambers, and of fin-rays ; a few irregular 

 spaces apparently represent the fin-ray lymph-spaces of other 

 genera. Oral sphincter underlies the angle of myotome 8. 

 Ten intra-buccal cirrhi are present. From twenty-one to 

 twenty-nine prseoral tentacles were counted. The nine most 

 ventrally placed are separated into two groups of four by 

 a single free median ventrad tentacle ; the two sets of four 

 ventrad tentacles right and left of the tentaculum impar pre- 

 sent a high intertentacular membrane, by which tentacle 2 

 (counting the impar as tentacle 1) is united to tentacle 3, 3 to 

 4, and 4 to 5 : the remaining tentacles on either side corre- 

 sponding to the numbers 6, 7, 8, 9, 10, &c., are free from one 

 another excepting for a low basal connection as in other 

 Branchiostoraidse. All the prajoral tentacles are smooth and 

 destitute of projecting sensory villi or papillse. Gonad pouches 

 twenty-six to twenty-nine, in a single series on the right 

 epipleur. 



