1(34 PROCEEDINGS : BOSTON SOCIETY NATURAL HISTORY. 
the Director of the laboratory, Prof. H. C. Bumpus, for much kind 
assistance in connection with this portion of the research. 
Coronary Arteries. 
The coronary arteries and the vessels with which they are 
directly connected reach a higher degree of complexity in the elas- 
mobranchs than in any other group of fishes, and consequently 
questions of terminology have arisen chiefly in connection with 
these forms. The system which we shall adopt is, in the main, 
an expansion of that employed by T. J. Parker (’84 and ’87) in his 
contributions to this subject, and its components may be briefly 
defined in the following way: The irregular, longitudinal artery 
by which the ventral ends of some or all of the efferent branchial 
arteries of a given side are brought into communication may be 
called the lateral hypobranchial artery (PI. 1, fig. 1, Ji’brn. /.). 
The arteries which leave the lateral hypobranchials on their median 
sides and, after more or less transverse courses, unite with one 
another in the median plane may be termed the commissural arter¬ 
ies (corns, iv-v). The longitudinal median trunk produced by the 
union of the commissural arteries may be designated the median 
hypobranchial artery (h'brn.m.). From the posterior end of the 
median hypobranchial, the coronary arteries (cor. v.) pass off to 
the heart. In the skates, there are in addition posterior coronary 
arteries (PI. 1, fig. 2, cor.p.s.). These arise from a vessel which 
is a branch of the subclavian artery and which from its proximity 
to the coracoid portion of the pectoral girdle may be called the 
coracoid artery (cc’d.). The coracoid artery, besides giving rise 
to the posterior coronary and certain small branches to the neigh¬ 
boring muscles, may anastomose with either the median or the 
lateral hypobranchial artery. 
The terms defined in the preceding paragraph agree in general 
with those used by Parker (’87), except in the case of the hypo¬ 
branchials. This author, to 'whom we are indebted for the name 
of these vessels, figured and described them as branches from the 
subclavians. After leaving the subclavians they give rise to the 
posterior coronaries, and, according to him, either they retain lateral 
positions, as in the skate, where they extend anteriorly to connect 
with the ventral ends of the efferent branchials of either side, or 
they unite in the median plane and give rise to a single longitudi- 
