16 
branched and articulated distally, but simple in the proximal portion ; fulcra 
small. Pelvic tins nearly as large as the pectorals ; dorsal and anal tins 
acuminate and opposed, the former short-based, the latter more extended ; 
caudal tin forked. Seales thin, deeply imbricating, and almost cycloidal, 
tliose of the Hank not deepened, and those of the dorsal and ventral aspect 
about as deep as broad ; conspicuous obtuse ridge-scales dorsally and ventrally. 
AiicirmoM/ENE tenuis, sj). nov. 
Plate II, Pigs., 5, G. 
I 
Ohs . — Three well-preserved specimens make known all the principal 
characters of the type species Archfconuenc, and may be enumerated thus : — 
(a) The type s])ecimen, a nearly complete fish shown of the natural size 
in PI. II, Pig. 5. 
(/>) Slab with two smaller fishes, the tail of one shown in outline, twice 
natural size, in PI. II, Pig. G. 
(e) Pi.sh (>07o in length. 
dhvo imperrect examples of the trunk of a mucli larger fish may also pertain 
to this s])Oci('s ; and if so it must sometimes have attained a length of at 
least 0-lS. 
Sp. Char . — The typc-species, commonly attaining a length of about 
0’12. Head with opercular apparatus occupying somewhat less than onc- 
fifth of the total length of the fish ; and the maximum depth of the trunk 
equalling about one-third of the length from the pectoral arch to the base of 
the caudal tin. Pectoral tin with from ten to twelve rays, the foremost 
especially stout ; pelvic 11ns arising midway between the pectorals and the 
anal, each with about six rays ; dorsal iin comprising about ten rays, arising 
behind the middle point of the back directly op])ositc to the origin of the anal, 
which has not less than fourteen rays. Scales exhibiting only the concentric 
lines of growth. 
Head and, Opercular Apparatus . — The head is scarcely as long as 
deep, and the cleft of the month is slightly oblique. The cranial roof is 
truncated behind and seems to have been originally niucli arched from side 
to side. The parasphenoid in its anterior portion, as it appears across the 
orbit, is very slender and slightly bulging downwards ; the premaxilhe are 
small, Avhile the maxillaries and dentaries arc conformed exactly as in 
