Fishes of the Western North Atlantic 19 



Generic Characters. Median finf old extending far beyond last myotome as a narrow 

 urostyloid process, with notochord reaching nearly to its tip; intertentacular membrane 

 much higher ventrally than laterally; ventral fin-ray chambers lacking in type species, but 

 perhaps present in others;'' caudal sector of median fin not demarked from more anterior 

 portions dorsal or ventral ; gonad pouches begin at myotomes 1 3 to 1 5 ; rostrum continuous 

 ventrally with both right and left sides of oral hood, and these in turn with each meta- 

 pleuron; atrial chamber extending behind atriopore as a pair of blind sacs; preoral tenta- 

 cles lack sensory papillae; no olfactory pit. 



Species. The type species of the genus is A. lucayanum Andrews, 1893, of the West 

 Indian region and Bermuda with which A. macricaudatum Parker, 1904, of Florida is 

 doubtless identical (pp. 19, 22); it is also reported from the Philippines. Our examina- 

 tion of its type specimens leads to this same conclusion for A . orientate Parker, 1 904, of 

 the Maldive Islands, Indian Ocean; nor does A. caudatum Willey, 1896, from the 

 Louisiade Archipelago, southeast of New Guinea, appear to have any better claim to spe- 

 cific recognition.'" 



Asymmetron lucayanum Andrews, 1893 

 Figure 3 A-E 



Study Material. Twelve specimens, from North Bimini I., Bahamas, and from 

 Vieques I., Porto Rico (U. S. Nat. Mus.). Five specimens (all of them types of A. macri- 

 caudatum Parker, 1904) from Salt Key, Florida (Harv. Mus. Comp. Zool., No. 26282). 

 Seven specimens (all of them types of A. orientale Parker, 1904) from the Maldive Is., 

 Indian Ocean (Harv. Mus. Comp. Zool., No. 32816). 



Distinctive Characters. The long, narrow caudal process marks this species off at a 

 glance from all other Atlantic Lancelets, from which it differs further in the still more 

 important morphological respects stated above (Key, p. 7). 



38. Whitley's (Aust. 2ool., 7, 1932: pi. 13, fig. 6) illustration of a specimen identified by him as caudatum Willey, 

 1896, and on which he based the new genus N otasymmetron, shows ventral fin-ray chambers, although he made 

 no mention of them in his description. 



39. A. caudatum Willey (Quart. J. micr. Sci., 59, 1896: 219, pi. 13, fig. 1-4) supposedly differs from A. lucayanum 

 in that its rostrum is marked off by definite notches or constrictions both dorsally and ventrally. But Goldschmidt 

 (Biol. Bull. Wood's Hole, 64, 1933 : 323, fig. la) has recently pictured the rostrum as of this same shape for a 

 specimen of /I. lucayanum from Bermuda, while we have seen one from the latter locality and another from 

 Porto Rico with a notch on the dorsal side, although with none on the ventral side. A. orientale Parker (Bull. 

 Mus. comp. Zool. Harv., 46, 1904: pi. i, fig. 4) was separated from A. lucayanum on the basis of a supposedly 

 narrower caudal fin. But no sharp line can be drawn in this respect between its type specimens, which we have 

 examined, and A. lucayanum of Florida and the West Indies (Fig. 3). We may also point out that the tail 

 region of one specimen, a male, described by Willey (1896) as A. caudatum was what may be termed the 

 "lucayanum" shape, that of the other, a female, of the "orientale" shape. It is possible, however, that the Aus- 

 tralian form identified by Whitley (Aust. Zool., 7, 1932: 260, pi. 13, fig. 6) as caudatum, and on which he 

 founded the genus N otasymmetron, may represent a distinct species, in which case a new specific name would be 

 needed for it; he has pictured it as having ventral fin-ray chambers, although these are not mentioned in his 

 description of it. We may further note that ventral fin-ray chambers are also indicated in the illustration of 

 A. lucayanum from the Maldives, by Forster-Cooper (in Gardiner, Fauna Geol., Maldive Laccadive Archip., /, 

 1903: pi. 18, fig. i). But no trace of such is to be seen in the Maldive specimens that we have examined; nor are 

 they indicated in Franz' (Jena Z. Naturw., 5J, 1922: 426, fig. 30) figure of a Philippine specimen. 



