288 



22 



The first basibranchial, cartilaginous in Aulostoma, is here a bone, with broad 

 and flat front end (PI. II, fig. 1 coM; it is the only basibranchial present. 



The gill arches are completely smooth, without any trace of gill-rakers or 

 teeth. The first arch is composed of 3 parts, a very short, clumsy hypobranchial, 

 a long ceratobranchial and a slender epibranchial; the second arch consists of 4 

 parts, a pharyngobranchial (ph") provided with teelh being present in front of the 

 slender epibranchial ; the third arch has also 4 parts ; its very slender epibranchial 

 is separated from the ceratobranchial and articulates distally both with ils own 

 and the following pharyngobranchial; the first (ph'") sends a process forwards 

 along the whole length of the preceding pharyngobranchial; behind this process it 

 is flat and beset with teeth. The fourth arch lacks the hypobranchial and the 

 epibranchial, its tooth-bearing pharyngobranchial being supported by the preceding 

 arch alone. 



The fifth, the lower pharyngeal is richly provided with teeth. 



As in Aulostoma the gills are continued on the pharynx wall, supported by 

 cartilaginous prolongations from the ceratohyals (PI. II, fig. 2). 



The reduction of branchial skeletal parts in Fistularia seems about to be 

 equal to that found in Aulostoma; only the epibranchials of the second and third 

 arches appear less reduced, as the latter alone is separated from the ceratobranchial. 



The following tabular view of the branchial apparatus in the two genera will 

 immediately show the fundamental likeness ". 



Aulostoma. 



Fistularia. 



The shoulder girdle (PI. Ill, fig. 8,9) has been fully described by Starks 

 (55 p. 630), and only a few remarks need be added. 



