Diodon rivulatus, _Cuv._ Mém. du Mus. tom. iv. p. 129. pl. 6.
An individual apparently of this species was picked up by Mr. Darwin on
the shore of the Rio Plata at Maldonado. It agrees with Cuvier’s
description, excepting that the undulating lines are not visible,
probably owing to the state of the specimen when found.
The spines are short, barely a quarter of an inch in length, but very
strong, compressed, and resembling canine teeth. There are three in
the first row between the eyes; about six in a transverse row across
the back, and seven or eight in a longitudinal one. Beneath they are
shorter and more numerous. The orbits are elevated in ridges, and
project forwards over the eyes. Two very small barbules attached to
the lower lip. Surface of the jaws smooth, the teeth not appearing as
scales.
D. 11; A. 10; C. 8; P. 22.
Length 5 inc. 3 lin.
As Cuvier observes, the _D. geometricus_ of Bl. and Schneid.[46]
approaches very closely this species, and I can hardly think it to be
distinct. Yet neither in Mr. Darwin’s specimen, which in all other
respects agrees exactly with Schneider’s figure, do I discern any
appearance of the hexagonal meshes on the surface of the body.