40 SMITHSONIAN MISCELLANEOUS COLLECTIONS [voL. 48 
and Ridewood) have associated with the Albulids. It has- been 
scientifically named Pterothrissus gisu and Bathythrissa dorsalis 
and may still be considered as the representative of an independent 
family, very closely related to the Albulids, but named Pterothris- 
side. The Pterothrissids are essentially like the Albulids but the 
branchiostegal rays are in reduced number (about six), the vomer 
and palatines are toothless, and the peculiar dentigerous bone which 
covers the basibranchials of the A/bula is undeveloped. The dorsal 
fin is prolonged over most of the back and caudal region. 
This family also is one of ancient origin, especially if Smith 
Woodward is correct in his statement that Pterothrissus “is not 
clearly distinguished from Jstieus.” Species of Istiews flourished in 
the seas whose deposits formed the upper Cretaceous beds of modern 
Westphalia and Mount Lebanon. 
Only one species (Pterothrissus gisw) is known from existing 
seas; it is a deep-sea fish which occurs at depths of three hundred 
to four hundred fathoms off the Japanese archipelago. Nothing is 
known of its habits. 
ABBREVIATIONS EMPLOYED IN THE LETTERING OF FIGURES (AFTER 
RIDEWOOD. ) 
al, alisphenoid. max, maxilla. 
an, angular. m, nasal. 
bb, dentigerous plate covering the of, opisthotic. 
basibranchials. Opc, opercular. 
bo, basioccipital. or, orbitosphenoid. 
br, branchiostegal rays. p, parietal. 
bs, basiphenoid. pb, pharyngobranchial. 
cb, ceratobranchial. pl, palatine. 
ch, ceratohyal. pm, premaxilla. 
cor, circumorbital bones. pof, postfrontal. 
ct, cartilage. pop, preopercular. 
d, dentary. prf, prefrontal. 
eb, epibranchial. pro, pro-otic. 
ecar, ectosteal articular. ps, parasphenoid. 
ecp, ectopterygoid. pt, post-temporal. 
eo, exoccipital. ptf, posterior temporal fossa. 
ep, epiotic. qd, quadrate. 
f, frontal. sar, sesamoid articular. 
gh, glossohyal. sm, surmaxilla. 
hb, hypobranchial. soc, supraoccipital. 
hh, hypohyal. sop, subopercular. 
hm, hyomandibular. sp, spicular bone. 
ah, interhyal. Sq, squamosal. 
top, interopercular. st, supratemporal. 
j, jugular or gular plate. stf, subtemporal fossa. 
me, mesethmoid. sy, sympletic. 
mpt, metapterygoid. v, vomer. 
