112 
PROFESSORS T. W. BRIDGE AND A. C. HADDON 
furnish strong confirmatory evidence in support of our provisional conclusions with 
regard to Acrochorclonichthys and Akysis. 
Olyra hurmanica, Day. 
The air-bladder in this species is said by Day (10, p. 711) to be “large, thin, 
and not enclosed by bone.” Brief as this description is, it may be legitimately 
inferred that the air-bladder is of the normal Siluroid type. 
Amiurus catus. 
Bamsay Weight (41 and 42) has described not only the condition of the anterior 
vertebrae in the adult, but also their development in very young examples of this 
species. These vertebrae are figured as seen in a ventral view and in longitudinal 
vertical section (42, Plate IV., figs. 7-8). Various sections, horizontal and transverse, 
through the cranium, auditory organ, and the anterior vertebrae of young specimens 
(3-4 cm. in length) are also represented [loc. cit., figs. 9-15), but no figures of the air- 
bladder or of its various skeletal attachments are given. We have dissected several 
examples of the species, and can confirm the accuracy of Ramsay Wright’s account 
so far as the adult Fish is concerned. 
Both as regards its skeletal modifications and the structure of the air-bladder, 
Amiurus exhibits a general resemblance to Pseudohagrus hracliysoma. The two 
species differ, however, in certain minor features. In Amiurus the centrum of the first 
vertebra is said to be provided with a pair of rudimentary transverse processes. The 
transverse processes of the fourth vertebra are somewhat more expanded than in 
Pseudohagrus, and their anterior and posterior divisions are less obviously distinct. 
The sixth vertebral centrum is not invested by superficial ossifications, and is therefore 
free. As is Pseudohagrus, there are no post-temporal plates. 
The air-bladder is normal. The primary transverse septum is wider than in Pseudo ^ 
hagrus. There are no secondary transverse septa, and unlike Pseudohagrus, the 
longitudinal septum is complete posteriorly. The skeletal attachments of the bladder 
are essentially similar to those of Macrones. Ramsay Wright {loc. cit.) describes the 
anterior wall as attached dorsally to the ventral edge of the transverse process of the 
fourth vertebra ; this attachment, however, is really the dorsal insertion of what we 
have hitherto called the transverse membrane into the anterior margin of the process, 
and does not implicate the proper anterior wall as in Arius and its allies. 
The scaphium is normal, but the intercalarium has neither ascending nor horizontal 
processes, and is represented by a small osseous nodule in the interossicular ligament. 
The tripus is also normal, but is without the heel-like process so characteristic of this 
ossicle in Macrones, and many of the preceding types. 
