360 Bashford Dean Memorial Volume 



its position and relations. The hypobranchials of the first pair are small and are situated 

 dorsal to the medial ends of the ceratohyoids. The second and third pairs of hypo- 

 branchials are distinct and well developed. The fifth and sixth pairs of hypobranchkls 

 are mere rudiments fused uith the basibranchials. 



Fiirbringer's specimen (1903, Fig. 18, Taf. XVID presents several features that are 

 different. A small median posteriorly directed prominence fused v.'ith the basfhyoid 

 may represent the first basibranchial, and a pair of posterolateral processes of the basihyoid 

 probably represents the first pair of hypobranchials. The second basibranchial appears 

 to be entirely absent, but there is a pair of second hypobranchials. The third basibranch- 

 ial is distinct from the fourth basibranchial, but is fused v.ith the fourth pair of hypo- 

 branchials. The fourth basibranchial is distinct from the fifth, but the fifth and sixth 

 basibranchials are fused together. The fifth and sixth pairs of hypobranchials are not 

 identified v^ith certaint^^ There is a vestigial seventh branchial element. Some features 

 of Fiirbringer's drawing are obscure, so that it is not suitable for reproduction here. 



Goodey (1910.1) described and figured (my Text-figure 26a) a small posteriorly 

 projecting prominence (bhr. 1 ?) on the basihyoid which, as in Fiirbringer's specimen, 

 probably represents a fused first basibranchial. Otherwise, Goodey"s drav-ing more 

 closely resembles that of Garman (1SS5.2). There are, however, some differences. "The 

 two lateral prominences [of the basihyoid], also at the posterior end, no doubt represent 

 the hypobranchials of the first branchial arch" (Goodey, 1910.1, p. 545). In Garman's 

 figure (my Text-figure 24) the hypobranchials of the first branchial arch appear to be 

 separate elements over-lapped by the ceratohyoids. 



Garman (1913) described and figured (my Text-figure 26b) this region of the visceral 

 skeleton in still another specimen. Here, there is no posterior projection of the middle 

 part of the basihyoid to represent a vestigial first basibranchial, but the other basibran- 

 chials are more numerous and regular than in any other specmien that has been figured. 

 There are five elements represented in this series, of which the fourth probably represents 

 the combined fifth and sixth basibranchials, while the slender posterior element may 

 belong to the vestigial seventh branchial arch discovered by Fiirbringer ^1903). The 

 first pair of hypobranchials Qihr. 1) is represented by posterolateral processes of the basi- 

 hyoid, while one member of both the second and the fourth pairs of hypobranchials 

 is fused with the corresponding basibranchial. The hypobranchials of the sixth pair 

 are small and are displaced somewhat posteriorly. The most posterior pair of cartilages 

 (r. hr. a. 7) presumably represent ceratohyoids of the seventh arch. 



AlHs (1923) agrees closely -w^th Garman (1885.2) in his description and portra^'al 

 of the basibranchials, but in the fourth branchial arch of his specimen he finds one of the 

 hypobranchials distinct and independent while the other is fused with the fourth basi- 

 branchial to form a single median cartilage v.^th a lateral process on one side only. This 

 fused hypobranchial is well shown in dorsal \^ew (^Figure 8, plate III), but is only partly 

 shown in a ventral view (Figure 9, plate III). The former figure shows also a pair of 

 rudimentary nodules representing the sixth hypobranchials, and both figures show a pair 

 of rudimentary seventh hypobranchials. 



