PARKER: MALDIVE CEPHALOCHORDATES. 47 



The collection from the United States National ]\rnseum, which I had the 

 privilege of stud\'ing, contained a few specimens of the West Indian Asym- 

 metron donated by Dr. Andrews, and I thei'efore had tlie opportnnity of mak- 

 ing a close comparison between this and the eastern form. As a result of this 

 comparison I found one structural feature in which the two sets of individuals 

 consistently differed ; this was the form of the caudal hn. In the West Indian 

 specimens as figured by Andrews (1893, Plate 13, Figs. 1, 2), and as seen in 

 the material before me (Plate 1, Fig 3), the dorsal and particularly the ventral 

 portions of the caudal tin in the vicinity of the myotomes were very broad, the 

 fin becoming narrow and blade-like only on the urostyloid process. In the 

 Maldivan forms (Plate 1, Fig. 4) collected by Mr. Agassiz, the ventral portion 

 of the caudal fin next the myotomes was only slightly broader than that under 

 the urostyloid portion, and the dorsal portion next the myotomes was no broader 

 than that over the urostyloid process. These features of the caudal fins in the 

 two forms were so characteristically different in the material at my disposal 

 that I do not hesitate to say that the seven Maldivan specimens certainly repre- 

 sent a species different from A. lucayanum, and I have therefore proposed the 

 name of Asymmetron orientale for them. 



While I am confident that the specimens collected by Mr. Agassiz are spe- 

 cifically distinct from A. lucayanum, I do not wish to be understood to imply 

 that this species may not occur in the Maldives. Although the seven speci- 

 mens examined by me have lengths not far from those of Cooper's S2:>ecimens, 

 they differ from the figure and description of these given by Cooper (1903, 

 2^. 348, Plate 18, Fig. 1) in the form of their caudal fins. The caudal fin, how- 

 ever, is an extremely delicate structure, and now that an important differential 

 character has been found in it, a re-examination of its condition in Maldivan 

 material heretofore supposed to be A. lucayanum would seem desirable before 

 declaring this species to be an unquestionable member of the Maldive fauna. 



Asymraetron macricaudatum, sp. nov. 



Plate 2, Fig. 7. 



Seven specimens of this species were in the collection of the Museum of Com- 

 parative Zoology. They were labelled " Salt Key Anchorage Fla." and were 

 probably dredged on" the Florida coast by the late Count Pourtalcs. Two of 

 the specimens were much curled and were of very little service for study ; the 

 remaining five were straight and in excellent preservation. The following de- 

 scription is based upon an examination of these. 



The specimens varied in length from 14.0 mm. to 10.5 mm. and were over 

 twelve times as long as they were deep (Plate 2, Fig. 7). 



The dorsal fin is low, particularly in its middle and anterior extent. From 

 the second myotome to a region somewhat posterior to the anus there are low 

 fin-ray chambers and short fin-rays. The fin-rays are generally block-like in 



