The head of the "P. pygmaea" is large and blunt. The head and nape are naked. The upper and lower profiles converge and are pointed if viewed from the sides. The head is characteristically broader than deep. The head is very short, broad and rounded. The mouth is very oblique, with a projecting lower jaw and chin. The posterior angle of the maxillary extends beneath the anterior part of the eye, up to the middle of pupil. It possesses two rows of teeth in each jaw. The outer row of teeth inside the upper jaw is larger and more widely spaced, while the inner row is characteristically minute. The first dorsal fin is low, much in advance of the second dorsal fin but not reaching the second dorsal fin when depressed. The pectoral and ventral fins are pointed, with the latter about as long as the former or longer. The anal papilla is very short and rounded in females, but is longer and very slender in males.