THE LATERAL CANAL SYSTEM. 363 



of which, indicated in the sketcli, is contiiuiou.s with the Literal line of the 

 body and another apparently with the cranial canal of the head ; and no 

 disks appear to be developed on the body. 



Meiiuccius anjiistiimtints and PJi^ciculus rastrclluja-, Plate LXXXIL, are 

 diverse forms w^iich probably are not well placed in the .same t'aHiily. Both 

 are Gadoids but J/. unfjuHtinyums exiiibits a lateral .sy.stem that difl'ers con- 

 siderably from that of its nearest allies in the Gadida3. Compared witli 

 them the arrangement is similar, there are no frontal branches of the cranial, 

 and there are two disks in each aural, but it is in peculiarities of the disk 

 that the dift'erences appear. Each disk is a broad band-like mass of tissue 

 on which there is a thin jellowish cover apparently granulated on the sur- 

 face and thicker in the middle, between the ends of the connecting threads, 

 in the position of the centrum. The centrum is not well differentiated, 

 though the glandular mass, in greater depth at this point, probaljly answers 

 its purpose; the fusiform portion of the disk was not to be detected. The 

 linings of the canals are pigmented, which with the lack of concentration of 

 the glandular tissue in a centrum may indicate differences in function. 

 There are 54 cephalic disks. The disks of P. radnllujer are like those of 

 other Gadida3 ; they are small, nearly uniform in size over the head, and 

 each aural, with two disks, turns sharply forward. The specimen possessed 

 6G disks on the head. 



3Iicrohpidiu)n grandlceps and Macrurus anguUccps, Plate LXXXIII. repre- 

 sent allied families which differ in regard to the amount of dependence placed 

 on the lateral system. 31. grandiaps of the Gadida3 was taken at the greater 

 depth, 1421 fathoms, but has less development in the disks, which are 

 small, and nearly uniform in size. Postorbital and spiracular series are 

 brought rather close togetlier in this species; no frontal branches were dis- 

 covered; there are two disks in each aural branch and 62 in the entire 

 cephalic portion of the system. In Macrurus anguliccjjs it is evident that 

 the function of the sj^stem is of more importance ; it has attained a much 

 higher degree of development, though the species was taken at a less depth, 

 10G7 fathoms. The minute disks in the frontal region illustrate the manner 

 in which as some of the disks increase in size their number is reduced, some 

 of them growing larger, others gradually disappearing. Including the obso- 

 lescent, there are 72 disks on the head of this species. On one of the spe- 

 cies on this plate the eye appears to be developed far beyond the system ; 

 on the other, eye and system are about equally important. 



