ESPECIALLY MYCTOPHOIDS 59 
total vertebral count is higher (80). The scale pattern would seem to be identical to 
that of the smaller specimens of Dercetis triqueter in which no expansion of the scales 
has occurred. Dercetis rostralis (Signeux) is a much more slender species than even 
Dercetis gracilis. The precaudal region has vertebrae at least six times as long as 
deep. The scute arrangement in this ‘neck’ region is also simplified, with only 
a single row of scales (lateral line?), whereas in the caudal region the more typical 
squamation of the genus is exhibited, i.e. three rows of scales. 
Genus RHYNCHODERCETIS Arambourg, 1944 
DiaGnosis (emended). Dercetidae in which the rostral region of the neuro- 
cranium is excessively elongated. Rostrum formed distally of premaxillae united 
in the mid-line. Mandible does not reach the anterior end of the premaxillae. 
Maxillae long, narrow and toothed, forming half of the gape. Teeth on dentaries, 
maxillae, palatines and ectopterygoids, but not on premaxillae. Paired fins reduced 
in size, pectoral fins on mid-flank region, pelvics arise behind the origin of the 
dorsal fin. Dorsal fin always short and midway along the body. Anal fin always 
short and remote. Two pairs of transverse processes on each precaudal centrum, 
the ribs articulating with the anterior pair. Dermal scutes reduced to a single row 
on each flank along the lateral line. 
TyPE-SPECIES. Rhynchodercetis yovanovitcht Arambourg. 
REMARKS. The genus was erected by Arambourg (1944) to contain the single 
species Rhynchodercetis yovanovitch, which is abundant in the Lower Cenomanian 
deposits of Morocco. Arambourg (1954) later expanded his original descriptions 
using new and more complete material from Morocco. Rhynchodercetis material 
from other localities is not abundant : Rhynchodercetis yovanovitcht has been 
described from Sicily by Leonardi (1966) ; Rhynchodercetis gortanii from Comen by 
d’Erasmo (1946) ; and Rhynchodercetis hakelensis from Hakel by Pictet & 
Humbert (1866). 
Rhynchodercetis hakelensis (Pictet & Humbert) 
(Text-figs. 27, 28) 
1866 Leptotvachelus hakelensis Pictet & Humbert : 98, pl. 14, fig. 3. 
1901 Leptotvachelus hakelensis Pictet & Humbert ; Woodward : 184. 
DraGnosis (emended). Rfynchodercetis of up to Io cm. in standard length. 
Vertebral column with approximately 60 vertebrae of which 30 are caudal. Head 
length equal to one-quarter of the standard length. Maximum height of the head 
equal to one-fifth of the total head length. Preorbital length of the head forming 
70% of the total. Dorsal fin with 7 rays, anal fin with 8 rays. 
HoLotyrPE. Minute, incomplete fish in the Museum dHistoire Naturelle, 
Geneva, from the Middle Cenomanian, Hakel, Lebanon. 
MATERIAL. One specimen, number P.6001 in the B.M.N.H., prepared by the 
transfer method. The specimen is poorly preserved as are the other minute speci- 
mens in the B.M.N.H. 
