64 THE DISCOBOLI. 



Anatomy. 



Details of the internal structure are given on Plate III. In Figure 1 

 the muscles and the lateral line system are shown as they appeared after the 

 removal of the skin. The tubes of the lateral sj^stem are almost entirely 

 cephalic, not extending behind the shoulder, as is the case throughout the 

 family, of which this species may be taken as a typical example. It is 

 evident from the limited extent of the tubes, and from the amount of mucus 

 over the entire body, that their function is not the production of the slime. 

 Considering them in connection with the presence of the disk, the position 

 of the eyes, the strength and expanse of the fins on the hinder portion of 

 the body, the kinds of crustaceans and fishes in the stomachs of this and 

 others of the species, and the habit of some to rest with the caudal extrem- 

 ity turned forward, it seems as if it might be within bounds to say that the 

 majority of these fishes are accustomed to lie in wait, anchored by the disk 

 upon rocks or other supports, to capture their swiftly moving prey by 

 sudden darts and rushes, and that, as in the Selachians, the lateral system 

 subserves the purpose of a very delicate tactile organ. With the reduction 

 of the gill openings there has been a corresponding diminution in the size 

 of the operculum, the movable cover of the branchial aperture. The skel- 

 eton, shown in Figures 3 and 4, though moderately firm, is comparatively 

 light. In most features, the skull compares well with that of L. pulchellus. 

 The crown is flattened; behind the orbits it appears subquadrate; it has 

 inconspicuous frontal ridges, with an interspace in the middle and a low 

 supplemental ridge a short distance farther back. The suborbital spine 

 is slender, and more than equals the length of the balance of the chain. 

 When Figure 3 was drawn, the slender postorbitals, connecting with the 

 postfrontals, would seem to have been overlooked. The operculum is 

 shaped less like a boot than in most of the species ; in outline it resem- 

 bles that of L. liparis. The angle in the middle of the suboperculum is 

 very blunt, and the expansion of the upper limb of the preoperculum is 

 less than that of L. mucosus. 



From the condition of the specimens it is possible to determine but little 

 about the viscera. The stomach appears as in the allied species; the cieca 

 are numerous, but may not be counted satisfactorily. 



