ESPECIALLY MYCTOPHOIDS 65 
(notably Ichthyotringa delicata, Text-fig. 5, p. 14), the tube within the frontal which 
contained the supraorbital sensory canal passes medially from above the sphenotic 
and then curves anteriorly to pass along the dorsal surface of the frontal above the 
orbit. This tube often appears to demarcate the medial frontal region from the 
lateral frontal region, the lateral region thus having the appearance of a separate 
bone. Arambourg (1954 : 108) also described and figured separate nasals. I was 
unable to find these as discrete elements in Rhynchodercetis hakelensis, where they 
appear to have become incorporated with the mesethmoid or lost altogether, both 
situations occurring in other teleosts. The mandible does not always terminate at 
the posterior end of the premaxillae as Arambourg indicated for Rhynchodercetis 
yovanovitcht. In certain of his specimens it definitely extends further anteriorly, 
almost to the end of the rostrum in fact, thus agreeing with Rhynchodercetis hakelensis 
in which the mandible extends to the anterior end of the palatine. Finally Aram- 
bourg (1954 : 111) describes and figures a prominent interoperculum. I was unable 
to find this bone in any of his specimens and it does not appear to be present in 
Rhynchodercetis hakelensis. 
Rhynchodercetis gortanii (d’Erasmo) 
(Text-figs. 30A—C) 
1946 Leptotrachelus gortaniu d’Erasmo : 76, pl. 1, fig. 4. 
1946 Leptotrachelus sp. (cfr. L. hakelensis) d’Erasmo : 82. 
1952 Rhynchodercetis acutissimus d’Erasmo : 108, text-figs. 7-12, pl. 2, figs. 4-6, pl. 3, figs. 1-4. 
D1aGnosis (emended). Rhynchodercetis of estimated standard length up to 22 cm. 
Vertebral column with 78-80 vertebrae of which 30 are caudal. Head equal to 
between a quarter and a third of the standard length. Maximum height of the head 
equal to one-sixth of the total head length. Dorsal fin with 8 rays, anal fin with 
16-20 rays. Pectoral fin with 10 rays, pelvic midway between the pectoral and the 
anal and composed of 8 rays. 
Hototyre. The holotype of Leptotrachelus gortaniui d’Erasmo, once in Bologna, 
could not be traced. The holotype of Rhynchodercetis acutissimus d’ Erasmo is in the 
Museo Civico di Storia Naturale, Trieste. Both specimens come from the Lower 
Cenomanian of Comen, near Trieste. 
MaTERIAL. Two trunk fragments from Comen in the Istituto di Geologia e 
Paleontologia della Universita, Bologna ; specimen number P.10913 in the 
B.M.N.H. ; and an incomplete specimen from the Natural History section, Prirodo- 
slovni Muzej Slovenije, Ljubljana, Jugoslavia. 
REMARKS. Leptotrachelus gortani was erected by d’Erasmo (1946) on a practically 
complete specimen from Gabrovizza in Comen, near Trieste. Together with the 
holotype d’Erasmo also used two trunk fragments from Dol Piccolo, also in Comen. 
The author has examined these latter specimens in Bologna but the holotype is 
missing. The holotype of Rhynchodercetis acutissimus d’ Erasmo (1952) together with 
several other body fragments, all from Comen, are in Trieste. Unfortunately these 
specimens were not made available to me but subsequently photographs of this 
