466 Bashford Dean Memorial Volume 



fuses posteriorly, in the median line, with its fellow of the opposite side, to form a single 

 median myelonic artery. The optic artery issues from the cranial cavity with the nervus 

 opticus and penetrates the eyeball with or near that nerve. 



My Text'figure 107 of Chlamydoselachus (after Allis) should be compared with 

 Text-figures 108 (after Daniel), and 109 (from Corrington, after Hyrtl), showing the 

 corresponding arteries for Heptanchus and Squalus respectively. 



The Branchial Arteries. — Either Ayers' (1889) figures (reproduced as my Text' 

 figures 105 and 106) are inaccurate, or his specimen of Chlamydoselachus was anomalous 



Text-figure 110. 

 Branchial, pseudobranchial and carotid arteries of Chlamydoselachus. 



aal, 11, etc., afferent arteries in the 1st, 2nd etc. branchial arches; acer, anterior cerebral artery; 

 ahy, afferent hyoidean artery; amd, afferent mandibular artery; apsh, afferent pseudobranchial 

 artery; cc, common carotid; cor., coronary; da, dorsal aorta; eal, U etc., efferent arteries in 1st, 

 2nd etc. branchial arteries; ec, external carotid; efiv, efferent hyoidean artery; epsb, efferent 

 pseudobranchial artery; ic, internal carotid; Ida, lateral dorsal aorta; om, arteria ophthalmica 

 magna; op, optic artery; peer, posterior cerebral artery; psh, pseudobranch; ta, truncus arteriosus. 



After AUis, 1911, Fig. 1. 



in this respect: only one efferent-collector artery is shown in each gill-arch, whereas in 

 all other specimens of Chlamydoselachus that have been examined, my own specimens 

 included, there are two such arteries. To be sure, Goodrich (1909, p. 137) wrote: "Ex- 

 cept in Chlamydoselachus, the branchial arches of the Selachii, like those of the Dipnoi, 

 have two efferent arteries;" but it is probable that Goodrich merely accepted Ayers' 

 account without verifying it. In his later (1930) text, Goodrich figures Chlamydoselachus 

 with two efferent arteries in each gill-arch. AUis (1908) at first accepted Ayers' de- 

 scription of the efferent branchial arteries, but later (1911) he prepared a figure (my 

 Text-figure 110) based on dissections of his own material, and commented (pp. 511-512) 

 on the results as follows : 



