FISHES. 251 



dal, and anal fins are almost greyish, througli the accumulation of the ahove mentioned dots. 

 The ventrals are unicolor ; the pectorals greyish upon their external margin. The abdominal 

 region sometimes exhibits an argentine reflection. 



Inhabits the lagoons in the vicinity of Santiago, Chile. 



Plate XXXIV, fig. 4, represents the profile of Cheirodon pisciculus, size of life. 



fig. 5, is a scale from the dorsal region. 



fig. 6, a scale from the lateral line. 



fig. 7, a scale from the abdominal region. 

 Figs. 5, 6, and 7 are magnified. 



FAMILY OF MYXINOIDEA. 



Genus BDELLOSTOMA, Miill. 



Gen. chak. Body eel-shaped. Anterior portion of head provided with four pairs of tentacles. 

 Eyes small. One hook-like tooth on the middle of the palate ; a double and arched series of 

 teeth upon the tongue. External branchial apertures from six to fourteen, corresponding to 

 as many gills, which are situated far behind the head. 



Syn. Bdellostmna, Mull. Abhand. Akad. Wis. Berl. (1834) 1836, 79, and (1838) 1839, 173. 

 Heptatrema, Dum. Zool. Anal. 1806. 



Obs. We refer naturalists to the memoir on the "Comparative Anatomy of the Myxinoids," 

 published in the Transactions of the Academy of Berlin for the years 1834 and 1838, for 

 information upon the internal structure of the fishes constituting the present genus. The 

 species which is described below might have furnished some interesting anatomical facts had 

 the specimen been in a better state of keeping. There are fourteen pairs of gills, seven more 

 than in either of the species previously known. 



The description of a Chilean species under a new specific name inay well raise the question 

 as to whether we had not before us the GastrobrancJms domheyi of Lacepede (Bdellosioma dom- 

 heyi, MlilL), of which very little is known up to the present time. Lacepede's description was 

 drawn from a dried specimen, no mention being made as to the number of respiratory aper- 

 tures. The anterior row of hyoidian teeth is composed of eleven teeth on each side, and the 

 posterior row of seven only, whilst in the one here described tliere are twelve teeth^ on either 

 side, in both rows. Moreover, as the eyes are said to be wanting in the species referred to by 

 the French ichthyologist, we did not feel justified in attempting, for the present, its identifica- 

 tion, since the absence of the organs of vision would even remove it from the genus Bdel- 

 losioma. 



It is to be regretted that Dumeril's appellation of Heptatrema, by referring to a point of 

 organic structure subjected to variations, could not be retained to designate these fishes gener- 

 ically. If that name be restricted to the species provided with seven respiratory apertures, 

 then each species would constitute a genus by itself; that with six of these apertures ought 

 accordingly be called Hexatrema ; then Heterotrema when six are observed on one side and 

 seven on the other ; Heptatrema when seven ; and finally Polytrema for the species described 

 farther on. 



Considering, however, the structure of the mouth, both internally and externally, we would 

 not hesitate in uniting them all under the well apjiropriated name of Bdellostoma, suggested 

 by Prof. Midler. 



