474 



DR. W. G. RIDEWOOB ON THE CRANIAL [DeC. 13, 



makes no attempt to support the great membranous interorbital 

 septum, neither does it send a process forward to meet the 

 prefi'ontals as it does in Clupea. 



Temporal and Preopercidar Series (text-fig. 134). — The post- 

 temporal has the usual three limbs. The longest is the upper 

 limb, loosely attached by ligament to the upper surface of the 

 epiotic. The opisthotic limb is delicate and rod -like, and is 

 attached, as already mentioned, to a process of the exoccipital, 

 there being no distinct opisthotic bone. The horizontal limb, 

 bearing the sensory canal, touches the back of the supratemporal. 

 The supratemporal has the usual triradiate form. The axis of 

 the preopercular slopes downward and backward, and its lower 

 limb is very short, and instead of being forwardly directed is 

 vertical. Tlae interoperculai- is remarkably small. 



pi 



Text-fig. 134. 

 •y* hrro 



cor 



pop 



p7W 



moc 



or srth 



Ewff7'aulis encrasicliolus, right side of skull. For explanation of lettering 

 see p. 493. 



Circumorhital Series (text-fig. 134). — The bones of this series 

 are six in number. The lai-gest lies below and behind the eye, 

 and above this bone are two small postorbitals. Both nasal and 

 preorbital, particularly the latter, ai-e relatively larger than in 

 Clupea. 



Maxillary Series (text-fig. 134). — The premaxilla is small, and 

 bears teeth on the posterior half of its lower edge. The two 

 premaxillfe extend, without meeting, below the mesethmoid, and 

 not in front of it as in Clupea ; it is, in fact, the projection of the 

 ethmoid region in advance of the mouth that gives the character- 

 istic appearance to the head of Engraulis. The maxilla is long, 

 and is toothed all along its edge except at the anterior end, where 

 it is overlapped by the premaxilla. There are two surmaxillte, a 

 broad one behind and a long thin one in front. They lie in an 

 extensible membrane which is continuous with the lower edge of 



