ESPECIALLY MYCTOPHOIDS 219 
a terminal half-centrum (ural vertebra 2). Preural vertebrae 2 and 3 both bear 
haemal spines which are slightly expanded and support the hypaxial accessory 
caudal rays. Only preural vertebra 3 bears a neural spine, preural vertebra 2 
merely supports an expanded neural arch. The fused vertebra (preural 1 and ural 
1) bears the parhypural (haemal spine of preural one) and the first two hypural 
bones ventrally. The centrum itself is slightly upturned. The parhypural is 
expanded and only has a small area of attachment with the centrum and anteriorly 
overlaps the haemal spine of preural vertebra 2. Hypurals 1 and 2 are sutured 
together, with hypural 1 being the larger. The terminal half-centrum bears a series 
of four hypurals supporting the upper fin rays. The stegural is borne on the dorsal 
Fic. 93. Aulopus filamentosus. Caudal fin skeleton in lateral view. 
surface of the fused centrum and consists of an elongate postero-dorsally directed 
strut, with an elongated expansion anteriorly. A second and possibly a third 
uroneural, both rod-like, occur postero-dorsally immediately behind the stegural. 
Three epurals are associated with the dorsal edge of the stegural. 
Nineteen principal caudal rays are present of which 17 are branched. Accessory 
rays are present epaxially and hypaxially, there being 16 in all. In front of the 
accessory rays a single large flattened fulcral scale is present above and below the 
peduncle. 
Scales. The entire body is covered with a uniform coat of regularly shaped, 
feebly ctenoid scales. The lateral line scales are slightly enlarged and bear a median 
ridge. In the head region the scales extend on to the cheek and the posterior end of 
the mandible. Scales also cover the rear end of the skull-roof as far as the parietals, 
and the anterior and posterior edges of the preoperculum, operculum and sub- 
operculum. 
