1914] Daniel: The Anatomy of Hetey^odontus francisci 155 



noted in those scales with a leaning spine. The arms of such a scale 

 are often not only unequal in size on the right and left sides, but also 

 unequal in numbers, being more numerous on the side away from 

 which the spine leans. Many such irregular scales may be found on 

 the rounded surfaces of the supraorbital crests; the spines of these 

 lean towards the median plane. 



Around the orbit in a young specimen there is present an inter- 

 esting modification of the dorsal type. These circumorbital scales lie 

 in a deep cavity, and more or less completely encircle the eye. As a 

 result of their location they themselves are protected, yet they doubt- 

 less serve to protect the eye, and in correlation with this function the 

 form of the scale has become modified in a direction opposite to that 

 of the supraorbital scales. The body of the individual scale is here 

 drawn out into a slender and almost vertical stalk terminating with 

 the spine. The direction of the tips of the circumorbital spines in 

 one of the specimens which I have studied — and one which shows these 

 scales in a most orderly arrangement — has the spine in all cases point- 

 ing away from the eye. Thus, those posterior to the eye point back- 

 ward, those above point upward, those below downward, while the 

 spines of the scales in front of the eye point foreward. 



Scales situated in the exposed area around the base of the spine 

 of the first dorsal fin (pi. 9, fig. 6) have become even more modified 

 than those of the supraorbital crests. To the naked eye these appear 

 as irregular, flattened plates closely packed around the base of the 

 spine. Under magnification these scales are seen to be modifications 

 of the dorsal type, in which the spine of the scale is absent, and the 

 body is so much depressed that the only mark of recognition of the 

 dorsal type is seen in the remnants of the arms. These, although 

 presenting great irregularity, show the various arms and in some cases 

 remnants of the crests characteristic of these arms. 



Still another modification of the dorsal type may be given. This 

 consists of scales which from their form may be designated as anchor 

 scales (pi. 8, fig. 3). These are located ventrally at the base of the 

 pelvic fins, and more or less laterally in the segment back of the cloaca. 

 The anchor scales are relatively few in numbers and of large size, 

 having the body elongated and the spine depressed. The anterior arm 

 of the scale, representing as it does the neck of the anchor fluke, is 

 especially long and heavy. Between the anterior and the lateral arms 

 there is a deep anterior niche on each side which runs well into the 

 lateral arms, giving to them the appearance of the flukes of an anchor. 



