12G 



THE ANATOMY OF VERTEBRATED ANIMALS. 



vvbicli thus seem to fringe a lobe of the integument. Hence 

 the fin is said to be lohate. In the other genera, only two of 

 the basal cartilages are present, and some of the radialia 

 come into contact with the shoulder-girdle between them. 

 In addition, the anterior dermal fin-ray is much larger than the 

 others, and becomes directly connected with the anterior basal 

 cartilage. Thus, in the structure of their fins, as in so many 

 other characters, the Ganoldei are intermediate between the 

 Elasonohranchii and the Teleostei. 



In certain Ganoids, as Lepidosteiis, Accipenser^ and many 

 fossil genera, the anterior margins of the anterior fin-rays of 

 the dorsal fins bear a single or a double series of small scales, 

 or spines, called fulcra. 



In A.ccipenser and Polypterus^ 

 spiracula^ or openings which com- 

 municate with the mouth, lie on the 

 top of the head, in front of the sus- 

 pensorium, as in many Elasmo- 

 branchs. 



Lepndosteus^ Accipenser^ and ^cci' 

 pirhynclius^ have branchiee attached 

 to the hyoidean arch, as in the Elas- 

 tnobranddi. They are now called 

 opercular gills. 



In Polypterus the air-bladder is 

 double and sacculated, and the pneu- 

 matic duct opens upon the ventral 

 aspect of the oesophagus. The air- 

 bladder thus becomes exceedingly 

 'like a lung; but its vessels are in 

 communication with those of the ad- 

 jacent parts of the body — not with 

 the heart, as in a true lung. 



In Lepidosteus^ the ducts of the" 



Fig. 42.— The female reproductive male and female reproductive organs 



Sf open frds'ofte •■gSit^i ^^e Continuous with those bodies, 



ducts; &, 6, oviducts; c, (7, the and each duct opcns into the dilated 



rij,'ht and left divisions of the , r> •, • i t xi j.i r^ 



urinan- bladder; e, e, the open- ureter ot itS SIQC. \Vi the other Gra- 



in{,'softhe ureters into the biad- ^oids the proximal cnds of the ffeni- 



der;./, the anus; g, g, the ab- , .1 - & 



doniinal pores ; A, the ui-ogenital tal duCtS, in DOtll SCXeS, Open Widely 



^P'^'"^"''"- into the abdominal cavity. In Fo- 



lypterus the united ureters open into 

 the cavity of the confluent oviducts, while, in the other Ga- 

 noids, the oviducts open into the dilated ureters. (Fig. 42.) 



