10 



dorsal, anal and caudal fins, when present, are always confluent ; their 

 rays are simple. 



This order embraces the " Eels" and (< Congers." The Electrical Eel 

 [Gymnotus *electricus Linn.) and the allied forms are excluded from the 

 order as they are true Teleocephali. In that order, there are many 

 geuera characterized by an elongated form and the absence of ventrals, but 

 none in which there is the union of characters indicated in the foregoing 

 diagnosis. In the present order alone is the absence of ventrals a perma- 

 nent feature. 



Order LEMNISCATI Kaup. 



This is a small order of doubtful affinity, and is composed of small fishes 

 which are destitute of ventral fins, and which are generally diaphanous, 

 greatly elongated and much compressed or ribbon-formed. An exception 

 is seen in the genus Helmichthys of Rafinesque, in which the body is vermi- 

 form or subcylindrical. The skull and vertebral column are incomplete 

 and cartilaginous. The blood is colorless, and there is no spleen. The 



"Ossacranii valida. solida, multa per anchylosin coalita. Ossa premaxil- 

 laria uiaxillseque desunt. Os nasi cum voineie ethmoideque in unum coalitum, 

 dentiferum, munus ossium premaxillarium sustinens ; os palati antice ad col- 

 umnam orbitse anteriorem ossi nasi per symphisin inhaerens, postice per ten- 

 dinem pedicello irno rnandibulse connexum ; cumque osse nasi rictum oris 

 superiorem conficiens. Mandibula longa, occiput postice sequans veltransiens. 

 Ejus pedieellurn tympanicum os unicum, validum, triangulare in latere cranii 

 late inhaerens." 



Richardson remarks that the nomenclature of the bones of the skull of these 

 fishes is a subject of no little difficulty, and he has gladly availed himself of 

 that proposed by Professor Owen in his Lectures on the Vertebrata. 



* The Gymnotoids are remarkable for the advanced position of the anus, 

 which is under the throat, and in the typical species of Rkamphickthys (Miil- 

 ler and Troschel) even before the eyes and between the limbs of the lower 

 jaw. But the advanced anus is not peculiar to those fishes. It also occurs in 

 the Aphredodei oids, and the Hypsceoids, both of which are North American 

 forms. The latter have now at least two, and perhaps three distinct genera 

 Amb'yopsis of Dekay, blind and provided with ventral fins ; Chologaster of 

 Agassiz, with eyes, but without ventral fins ; and Typlichihys of Girard, ap- 

 pearing to differ from Chologaster only by its rudimentary eyes. It may be 

 doubted whether the last two are distinct. 



They bear nearly the same relation to each other that the "crawfish" of 

 the Mammoth cave does to the numerous species found in our streams. Yet 

 no carcinologist has attempted to generically distinguish the one from the 

 others. All are for them true Cambari. There is an atrophy of a single organ ; 

 all other parts of their organization are similar. The single modification is 

 adapted for a special purpose; tofitthemfor a peculiar habitat; there is no need 

 of the organs or the sense, and they have been therefore withheld from them. 

 As the modification is determined by habitat and not independent of it, it has 

 scarcely a generic value unless accompanied by some other peculiarity. 



Bourguignat in the " Revue et Magazin de Zoologie " for 1856, (vol. viii. p. 

 499) has established a genus, which he has named Zospeum, for a group of ter- 

 restrial Gastropod Mollusks peculiar to the caves of Central Europe. Its spe- 

 cies had been previously by most naturalists referred to Carychium. 



