ON THE ANATOMY OF FISHES. 
183 
Hupostomus uen'es, Cuv. and Val. (= Flecostomas veryasY) 
According to Keissner (32) this species agrees in all Important details with 
Loriccu'ia, but has a more perfectly formed “processus bijugus.” 
These statements we are able to confirm. In the condition of its anterior vertebrm 
and in the mode of formation of the osseous capsules for the two air-sacs, as well as 
in the absence of a bony roof to the recess for the sacculi and the cavum sinus 
imparis, Plecostomus closely agrees with Loricaria. 
We have satisfied ourselves that the “ processus bijugus” in Plecostomus supports 
the slender intermediate canal by which the two air-sacs are placed in communication 
with each other. In this respect Plecostomus confirms Reissner’s suggestions tis to 
the object of this singular structure in Acanthicus. 
We could detect no trace of either intei’calaria or claustra. 
. Callichthys aspev. 
Of this species Reissner (32) remarks that he had only a very small and badly 
preserv^ed specimen for examination. In the structure of the cranium and the 
condition of the “first” vertebra, the air-bladder and Weberian ossicles this Siluroid 
is said to be more closely allied to Plecostomus than the latter is to Loricana. The 
“processus bijugus” is said to be similar to that of Plecostomus, and in connection 
with its arch Reissner found a minute canal which, he adds, probably served the 
purpose of uniting the two divisions of the air-bladder. The tripus is slightly bent, 
and divides anteriorly into two processes, one for attachment (articular process), and 
the other for connection with the deeply concave scaphlum. 
As far as we were able to determine from the external examination of a Museum 
skeleton of Callichthys littoralis, this species closely resembles Loricaria in the 
modifications which the anterior vertebrae undergo, and in the mode of formation 
of the osseous capsules for the air-bladder, but the union of the vertebral column 
with the skull seems to be more intimate than in either Lo)‘icaria or Plecostomus 
[Ilypostordus). 
Sisor. 
Without reference to any particular species. Day (‘J) thus refers to the condition 
of the air-bladder in this genus : — “ Subvertebral bony capsules were present, and 
apparently contained an air-vessel, whilst none could be detected in the abdomen.” 
Pseiulecheneis. 
Of this genus the same observer (9) remarks that the air-vessel is “ in two rounded 
lateral portions, and enclosed in bony capsules.” 
