336 



ferior mass cannot be considered as a part of the same 

 stratum as the transversalis since the latter sends its 

 terminal fascia dorsalward to this mass. Here then is 

 another point in which Amphiuma differs from the 

 other members of its class. 



The conical arrangement of the muscles prevails not only in the 

 dorsal portion of the tail of Amphiuma but also in the ventral 

 portion. The disposition and attachments of the cones here are so 

 very similar to those of the trunk region that it would be unprofi- 

 table to describe them. The number of cones in this region is ap- 

 proximately four hundred and sixty eight though some of them near 

 the extremity are rather imperfectly formed. The whole number in 

 the trunk counting twelve to each vertebra equals seven hundred and 

 forty four, which added to the four hundred and sixty eight in the 

 caudal region, gives a total of one thousand, two hundred and twelve 

 cones. In other words, the dorsal and caudal muscles 

 of this animal have over one thousand strong fascial 

 attachments. 



Having discussed the general structure of these muscles it is now 

 in order, to determine the direction of the fibres. These are not 

 parallel to a line through the apices of the cones, as we should ex- 

 pect, but are so directed as to form an angle of about ten degrees 

 with that line. Since there are no cones found in the outer half of 

 the dorsal muscle, the direction of the fibres there, is exactly parallel 

 with the axis, being, however, completely interrupted by the inscrip- 

 tiones tendineae. 



I shall not attempt any mechanical explanation of this peculiar 

 structure of Amphiuma in this brief contribution, but will reserve 

 that problem for a later article and here only add that so far as I 

 have been informed, this conical disposition of the fibres has been 

 observed only in two other vertebrates. Dr. Hair (Journ. of Anat. and 

 Physiology Vol. II) represents a similar formation of cones in the 

 Alligator and that the same structure is prevalent in the 

 dorsal muscles of Spenoden (Hatteria) the peculiar 

 New Zealand amphibian-like lizard. 



Princeton, Jan. 25th, 1894. 



