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Bashford Dean Memorial Volume 



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sure, Ayers notes the absence of such loops in his specimen, but they are shown in 

 various figures by AUis (1911 and 1923). In Chlaynydoselachus a posterior efferent' 

 collector may retain a dorsal connection ^-ith the anterior efFerent-coUector of the same 

 gill (^Text-figure 110), an arrangement not usually found in adult elasmobranchs though 

 commonly present in their early embryos. 



As portrayed in Text-figure 110, the afferent branchial arteries of Chlamydoselachus, 

 excepting the hyoidean and the last branchial, bifurcate dorsally, one branch passing 

 over the cleft anteriorly to join the afferent in front, the other passing posteriorly over 

 the succeeding cleft to join the follov.'ing afferent. Thus the afferents, like the efferents, 

 are connected into a series of loops around all the clefts. Complete afierent loops are not 

 found in other sharks. Basing his opinion upon what is knouTi concerning the manner 

 of development of the branchial arteries in other sharks (particularly in Squalus as de- 

 scribed by Scammon, 1911), Corrington (1930) concluded that the anastomoses which 

 complete the afferent loops around the gill-clefts in Chlamydoselachus could arise only 

 late in embryonic development, after the arterial pattern had been nearly completed; 

 therefore they are among the most recent acquisitions of the branchial arches. They 

 represent a secondary' and speciaHzed condition — an interpolation — in Chlamydoselachus, 

 and are probably incipient in Heptanchus (Text-figure 111). 



In elasmobranchs generally, each epibranchial arten,^ of the early embryo is situated 

 dorsal to a gill-arch; but in later development these arteries become shifted to positions 

 dorsal to the respective gill-slits (Goodrich, 1930, Figs. 531a-d and 532). In Chlamy- 

 doselachus, the epibranchial arteries of the adult (Text-figure 110) are situated dorsal to 

 the respective gill-arches — that is, they retain what is presumably their embryonic 

 position. According to AUis (1912) they are ver>^ nearly in the same position in Heptan- 

 chus (my Text-figure 111\ 



Corrington (^1930, p. 198) suggests that, since Daniel has given us the apt desig- 

 nation of efferent-collector artery for the lower forks that gather up the oxygenated blood 

 from the gills, we may restrict the name efferent branchial artery to the upper and single 

 trunk, thus expressing its revehent correspondence to the afferent branchial artery in 

 their relationships to the gills. Epibranchial thus becomes a synonym for efferent bran- 

 chial. Concerning the efferent branchial (epibranchial) arteries in elasmobranchs, 

 Corrington (pp. 198-199) writes as follows: 



The first of the series is the efferent hyal artery which courses forward and has been . . . 

 long identified with the carotid system. . . . Then follow 4, 5 or 6 efferent branchials, de- 

 pending on the species, and confonning to the number of giUs and of afferents, as previously 

 noted. Usually these are all separate, but in j<lotorhynchus, Heptranchias [Heptanchus], 

 Chlamydoselachus and doubtless in other notidanids, the last efferent joins the penultimate 

 midway of its course so that the two have a common stem thence to the aorta. The condition 

 indicates the approaching loss of the last giU in each case, and is a parallel circumstance to 

 the fusion of the pharyngobranchials of the last tw,-o skeletal arches, so commonly seen in 

 sharks. 



