FOSSIL AND RECENT 177 



The anterior end is shallower than the posterior end. The posterior ceratohyal is 

 thinner than the anterior element. The ventral margin of the posterior ceratohyal 

 is curved while the dorsal margin is straight, except posteriorly where the border 

 is notched for the reception of the interhyal. Both dorsal and ventral hypohyals 

 may be identified but little of their shape may be seen. Each hypohyal consists 

 of a core of spongy bone covered by a thin perichondral shell. The anterior tip of 

 the hypohyals lies between and level with the lower jaw articulation when the 

 mouth is closed. The dorsal edge of the anterior ceratohyal is grooved for the afferent 

 hyoidean artery. The depth of this groove is comparable with that seen in Albula. 



There are 12-14 branchiostegal rays. The first (or most posteriorly situated) 

 branchiostegal is broad and supported solely by the posterior ceratohyal. The 

 second of the series articulates with the hyoid bar at the junction of the two cerato- 

 hyals. The branchiostegals become progressively thinner at the anterior end of the 

 series. Anteriorly, the last ray in the series may have lain free in the branchio- 

 stegal membrane since it is often displaced and shows no development of an articu- 

 latory head. 



A large gular plate is attached to the posterior edge of the dentary symphysis. 

 The width of this plate, equivalent to over one-third of the mandibular length, 

 suggests that the lower jaw rami were wide apart. It is significant that in many 

 specimens the jaw rami are often seen splayed apart. The size of the gular plate 

 would preclude any interpretation of the gular lying vertically as it does in the 

 Recent Albula. 



The basibranchial and basihyal elements are poorly known. A large basibranchial 

 tooth plate lies in a position (with respect to the hypobranchials) suggesting that it 

 represents the fusion of the first three basibranchial plates. The dorsal surface of 

 this plate bears many villiform teeth. The posterior end of a basihyal tooth plate 

 is seen in B.M.N.H. P. 4764. The plate appears edentulous. 



The hypobranchials of the first three arches are developed in typical fashion. The 

 first is the longest of the series and shows a slight curvature. The second, like the 

 first, shows a distinct basal articulatory head proximally, but the short third hypo- 

 branchial appears merely as an ' outpushing ' from the third basibranchial. The 

 five ceratobranchials are typical in that the first is substantially longer and broader 

 than the fifth. The latter elements share a small mutual interface. Small, irregular 

 tooth plates, each with many needle-like teeth, are associated with the oral surfaces 

 of the ceratobranchials. These tooth plates are relatively sparse : for instance 

 six are detectable upon the fourth ceratobranchial of B.M.N.H. P. 4764. A single 

 large tooth plate is associated with the medial margin of the fifth ceratobranchial. 

 This tooth plate, the lower pharyngeal, has the shape of an isosceles triangle, twice 

 as tall as wide with the apex directed anteriorly. 



Well-defined gill-rakers were not seen on any but the first ceratobranchial. The 

 gill-rakers have the same form as those of Albula and Pterothrissus. Nothing of the 

 dorsal gill arch elements was seen. 



Circumorbital bones. The supraorbital was not positively identified in any speci- 

 men but several exhibit small splinters of bone indicating that its form was as in 

 Recent albuloids. 



