1894.] HTOID ARCH OP CERATODTJS. 639 



ligament, more strongly developed than in Ceratodus, running 

 upwards and inwards from the upper and inner end of the ceratohyal 

 to the base of the skull at the side of the parasphenoid. 



There is no basihyal nor hypohyal, but the lower ends of the 

 ceratohyals are connected by ligament. 



No cartilage which might correspond with the hyomandibular of 

 Ceratodus is to be distinguished. 



Owen (7), evidently describing an improperly articulated skull, 

 writes : " a strong cylindrical and almost straight styloid bone is 

 articulated by a somewhat compressed and expanded upper extre- 

 mity to the cartilaginous petrous element of the temporal ; it extends 

 downwards and forwards, parallel with the as tiimpanicum ^ and is 

 articulated to the upper part of the expanded posterior extremity 

 of the ceratohyoid bone." The ceratohyal is named correctly, but is 

 unfortunately articulated with the lower end of the cranial rib, 

 which, in the figure, is made to point forwards instead of backwards 

 and is called " styloid." 



Writing later (8) in 1866 he adopts Bischoff's (1) view that 

 this latter bone is the suspeusor of the pectoral girdle, for, in his 

 fig. 41. no. 51, it is called scapula and is articulated at its lower 

 end with the shoulder-girdle, which is called coracoid. 



Two years later Parker (9) described it as the first pharyngo- 

 branchial ; and it was left to Giinther (4) in 1871 to demonstrate 

 that this bone, which had suffered such vicissitudes of^nomenclature, 

 is simply the first rib wliich has acquired a secondary connection 

 with the skull. 



There are no careful descriptions of the hyoid arch of Lepidosiren, 

 but it may be concluded that it differs but little from that of 

 Protopterus. 



Briihl (2) (Taf. Ixiii. Kg. 8, Punkt 2) speaks of an articular 

 cavity in the postero-external border of the chondrocrauium for 

 insertion of the hyoid apparatus ; and Hyrtl (6) states that the 

 hyoid is attached to a blunt process of the quadrate, and that the 

 ventral ends are united by a rigid synchondrosis and not by a 

 ligament as in Protopterus. 



Giinther (4, p. 526) mentions the absence of basihyal and 

 glossohyal (i. e. the elements named in this article the hypohyal and 

 basihyal). 



We may, happily, now look forward to more minute descriptions 

 of the visceral skeleton of this once rare Dipnoan in the publications 

 of the numerous investigators who are prosecuting their researches 

 on the specimens recently collected by Dr. Bohls in Paraguay. 



A careful examination of the hyoid system of living Dipnoi leads 

 one to conclude that there is no connection between the reduction 

 of the hyomandibular in these fishes and its adaptation as a secondary 

 suspensorium in the Elasmobranchii (excluding the Holocephali) 

 and the osseous fishes, and there appears to be very Uttle evidence 

 in support of Gadow's view (3, p. 459) that the reduction of the 



^ Pre-opercular. 



