FISHES. 101 



and those which the mind of the American or European pictures to itself in connection 

 with the name. But those common species exhibit structural features from which 

 most of the order deviate, and they at the same time depart less from the character- 

 istics of ordinary fishes than do most of their associates. Their bones are developed 

 in greater number than in most of their relations, and there is a nearer approach in the 

 osseous frame-work generally to the typical fishes. The congers, or conger-eels, are, 

 however, as little aberrant as the true eels. But, with these exceptions, the species of 

 the order generally to be met with exhibit remarkable modifications of structure, and 

 a notable reduction of the bones of the sides of the head. So great, indeed, are the 

 differences to be seen on a comparison of the true Apodal or eel-like forms, that 

 they have been distributed by an eminent authority (Professor Cope) between two 

 orders, the Enchelycephali (eels and congers), and the Colocephali (Murtenids, etc.). 

 Other forms have been associated with the eels, but with little reason. Few nowadays 

 would consider the electrical eel to be closely related to the true eels, and therefore 

 few would dissent from excluding it from the order Apodes, if intended to be grouped 

 primarily around the common eel. There are also quite good grounds for the refusal 

 to admit the Monopterids and Symbranchids in the same natural order as the Anguil- 

 lids, but the differences between the last-named fishes and the Murffinids ajDpear to be 

 of less value, and gradations exist between them. For the present at least, therefore, 

 all such may be retained in a common order under the name Apodes. 



The Apodes may then be defined as teleost fishes with the ethmoid and vomer 

 coalesced and constituting the front of the upper jaw, the supramaxillaries entirely lat- 

 eral, and the intermaxillaries obsolete or wanting, the palato-pterygoid arch more or 

 less imperfect, the cranium with a single condyle (the basioccij)ital) for articulation with 

 the backbone, the branchiostegals well developed, and the form elongate and serpenti- 

 form. 



The fishes in which these characters are manifested are all elongated, and the form 

 may consequently be used for the definition of the group. Nevertheless, it must not 

 be forgotten that form is an extremely variable element in some orders, and even in 

 the present the eel-like appearance is not invariably a striking feature. The curious 

 Simenchelys, for instance, was not at first recognized as an eel by the ichthyologists 

 into whose hands it fell, and it was only when the structure of the mouth parts was 

 examined that its position became evident. On the whole, however, there is a very 

 considerable likeness between the various constituents of the order, so far, at least, as 

 general foi-m is concerned. The skeletal and other differences are better marked, and 

 apparently justify the recognition of several families. 



The Anguillid^, or typical eels, have the ethmo-vomerine region moderately 

 broad and extended backwards, the jaws rather elongated and narrowed forwards, the 

 opercular bones all existent, the pterygoid bones reduced and slender, the tongue 

 free in front, the nostrils moderately distant and lateral, the caudal fin developed and 

 confluent with the dorsal and anal, the dorsal remote from the head, and pectorals 

 present. Scales are present, of small size and elliptical form, obliquely set, more or 

 less separated from each other, and tending in opj)osite directions, or at right angles 

 to each other. But one genus of the family thus defined has been recognized, the 

 genus Anguilla. The species have not been determined with certainty, some natural- 

 ists having recognized as many as forty-nine species (Kaup), another (Gtinther) about 

 twenty-five species, while a more recent student (Dareste) has thought that not 

 more than four valid species can be discriminated. The four recognized by Dareste 



