DESCRIPTION OF A SILURUS. 
379 
inches ; that of the pectoral spines nearly 6 inches. Besides 
its bony spine, there are seven rays in the first dorsal fin ; 
but there are no rays in the second, which is adipose, but 
not very thick. The number of rays in each pectoral fin, 
exclusive of the spine, is eleven. The two ventral fins are 
S inches apart, and each of them seems to have six rays. 
The ventral and anal fins have a deep red colour in the re- 
cent fish. The latter has 18 rays. The tail is deeply forked, 
and has SO rays. The lateral line is slightly waved. The 
air-bladder lies below the heart-shaped bony shield, and is 
attached to the first vertebra. Its form is best expressed 
by the accompanying figure (Plate VI. Fig. J. a.). 
It is to be regretted that the descriptions of scientific 
travellers and of naturalists are often too concise to enable 
us to discriminate with certainty the animals they meet 
with. The Silurus now under consideration has some 
afiinity to the tS. Felis, S> Catus, S. galeatus, and S. Herz- 
herglij as noticed in Shaw's Zoology, and other works ; but 
its bony casque, and the armature of its fins, seem to discri- 
minate it sufficiently from the two first. Its size, forked 
tail, its heart-shaped nuchal plate, and the number of rays 
in its anal fin, distinguish it from the third species ; while 
its colour, casque, and the position of the adipose fin, pre« 
vent us from confounding it with the last, unless I am de- 
ceived by the imperfection of the descriptions of our syste- 
matic writers. 
Conceiving it to constitute a new species, I would pro- 
pose to name it in honour of its discoverer, who, in a short 
visit to Guyana, undertaken for other objects, has zealously 
applied himself to illustrate the natural history of that 
country. It may have the following specific character : 
