379 



front chamber alone persisting (Clarias, Saccolranchus, Bagarius, Loricariidae, 



etc.). In some (Aucheniptems, etc.) a peculiar elastic spring apparatus is 



developed from the expanded parapophysis of the fourth vertebra, which 



acquires a thin pliable base, ami can be moved by muscles so as to alter 



the pressure in the bladder and produce a sound (J. Mu'ller, Bridge and 



Haddon [58]). There are no pyloric caeca. Accessory respiratory organs 



are sometimes developed. Certain anterior lepidotrichia in the dorsal and 



pectoral fin may become modified 



into powerful spines (Bagrinae, 



Doradinae, etc.), connected by an 



elaborate locking joint. InAmiums, 



for instance, the first interspinal 



plate is a small ossicle with its 



dermal ray a small scute ; the 



second ray is a U-shaped bone 



at the base of the large defensive 



spine, which is the third dermo- 



trich resting on a large plate 



belonging to the third radial. In 



the Bagrinae and Doradinae there 



is a regular dorsal buckler thus 



formed in connection with the 



dorsal fin (Fig. 366). 



Callomysta.'- produces a stridu- 

 lating sound by the scraping of the 

 first dorsal radial between the 

 ridged laminae of the deep cleft of 

 the combined fourth and fifth 

 neural spines (Haddon). 



The Siluroidei present some 

 most striking superficial resem- 

 blances to the extinct Cephalaspidae 

 and Coccosteidae. So close is the 

 likeness (especially among the 

 Clariinae and Loricariidae) as even 

 to deceive so acute an observer 

 as Huxley [227]. It is now FIG. 865. 



generally admitted that the resem- . Auchenogianis biscutatis, Geoifr. A, ventral 



, view of the pectoral girdle ami left pectoral hn. 



blance between these Siluroidei B, ventral view of the pelvic girdle and left 



ind the Dpvoninn fossils is dnp tn P elvic fln - clt > cleithrum ; co, coracoid ; msr, 



3 mesocoracoid ; p, pelvic bone ; pf, pelvic lepido- 



COllVergence. trichia; .*;>, pectoral spine or first lopidotrich. 



Family SILURIDAE. These fish 



usually have an adipose fin. The tail region is extremely long in the 

 Clariinae, where both the anal and the dorsal fins are extended ; and in 

 the Silurinae, where the dorsal is very short and the anal very long. 

 The opercular bones are somewhat reduced. 



Clarias has accessory respiratory organs in the branchial cavity 

 (Fig. 368) ; and in Saccobranchus a large diverticulum, supplied 

 with blood from the aortic arches, extends back from the branchial 



