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CAPTAIN E. W. SHANN ON 
( b i) Levator pectoralis is wanting in the Sturgeon. 
B. Connections with the Visceral Arches. — In further correlation with the 
relative immobility of the shoulder girdle, these muscles are fewer in number and 
smaller in extent than in other groups of fishes. 
( b ii) Cleithro-branchialis.* 
This is a compact, strap-like muscle which, inserted on the base of the fifth 
branchial arch, runs outwards and downwards, spreading slightly fan- wise to its 
origin on the inner aspect of the lower third of the cleithrum. 
(■ b iii) Claviculo-hyoideus. Coraco-arcualis posterior, Vetter, Ostroumoff. 
This muscle arises from the ventral anterior border of the clavicle and is inserted 
at the base of the hyoid arch. Unlike the condition in most Elasmobranchs, this 
muscle is not divided by myocommata ; according to Ostroumoff, it is formed by a 
ventral outgrowth of the third myotome. 
The very minute branchio-mandibularis (fig. 14, Br.mn.) of A. rubicundus appears 
to be a vestige of the coraco-mandibularis so characteristic of Elasmobranchs. 
2. The Pectoral Fin. 
The details of the fin musculature have not been worked out, but the general 
composition is diagnostic. Both the adductor and abductor muscles are divided into 
two layers, a superficialis and a profundus. The fibres of each of these muscles are 
collected into distinct bundles for insertion on the fin rays. 
Davidoff (20) found a similar condition in the pelvic fin of A. ruthenus, except 
that the abductor was not divisible into two superimposed layers. 
IV. Teleostei. 
(See List of Types, p. 532.) 
1. Shoulder Girdle. 
(l) The Lateral Muscle. 
A considerable time was devoted to the study of this muscle, and the results are 
recorded in the Proceedings of the Zoological Society of London , “ On the Nature of 
the Lateral Muscle in Teleostei,” 1914, p. 319. 
(2) The Posterior Muscles. 
(a) Retractor latero-dorsalis pectoralis. Retractor scapulae, Owen. — The latero- 
dorsal portion of the lateral muscle is inserted at its anterior extremity on the side 
* It is interesting to note that the Cleithro-brancliialis is single in Accipenser, while in Polypterus it is divided 
into three distinct parts (fig. 24). Both these types differ in respect of this muscle from the condition whieh is so 
constant.throughout the Teleostei. 
