406 STRUCTURE AND CLASSIFICATION OF BIRDS 



As regards the other leg muscles Phaeton has quite excep- 

 tionally no tendinous loop for the biceps to pass through. 1 



The plantar tendons blend in Fregata, &c., sending slips 

 to all four toes ; they blend in Phaeton, but send no branch 

 to hallux. In Plotus there is no blending, but a strong 

 vincnlum, which is attached to flexor perforatus, just as it 

 splits up into its three branches. This too is the case with 

 Phalacrocorax, but the vinculum is not strong. 



In the pelicans (at any rate in P. rufescens and P. 

 mitratus) there is a curious relationship between the femoro- 

 caudal and the semitendinosus. The former receives a tendi- 

 nous slip not far from its insertion, which runs up from the 

 middle of the semitendinosus at right angles to its fibres. 

 Whether this may be regarded as a rudiment of the accessory 

 semitendinosus or not is uncertain. 



Another peculiarity shared with Biziura lobata, Colymbu*, 

 and the extinct Hesperornis is the perforating of the patella 

 by the tendon of the ambiens in Phalacrocorax. In Plotu* 

 there is a groove upon the ossified patella, and, remarks 

 Professor GAEEOD, ' some of the fibrous ligament overlapping 

 this groove shows traces of ossification ; so that in aged birds 

 this groove may be converted into a foramen.' 



Gluiceus I. in the Steganopodes is a small muscle, not 

 extending, or hardly extending, over the biceps. Glutceus 

 V. is large. In Fregata glutasus I. is absent. 



The form of the syrinx of the Steganopodes varies con- 

 siderably, but in all it is trach Go-bronchial ; intrinsic muscles 

 may be present or absent.-' 



Of Pelecanus I have examined six species, viz. P. niitratu*, 

 P. onocrotalus, P. rufescens, P. fitscus, P. conspicillatus, and 

 P. crispus. In none are there any intrinsic muscles, and the 

 bronchidesmus appears to be complete. 



In P. conspicillatus the organ of voice is very simple. 

 The rings are but little modified. There is a bony pessulus, 

 which is attached behind to the last two tracheal rings, 



1 This peculiarity is, however, to be found in the swifts. 



2 The anatomy of Pelecanus rufescens has been described by OWEN, P. Z. S. 

 1835, p. 9, by MARTIN, ibid. p. 16, and by ALIX, loc. cit. on p. 40:5, above. 



