N. ROSÉN, STUDIES ON THE PLECTOGNATHS. 



11 



former layer contains very few fibres. Star-shaped chroma- 

 tophores line the basal membrane. The interiör portion of 

 the corium consists of an enormous number of fibres collected 

 into bundles, anastomosing with each other. They run in 

 several different directions. Almost all of them take part in 

 making up the lower portion of the plates. Only a few are 

 not calcified and form a thin interiör stratum of the corium, 

 the inner surface of which is dotted with a dark pigment. 

 No subcutaneous tissue is developed (Fig. 7 and 8). 



Integumental ossifications. (Fig. D— F). The integu- 

 mental ossifications have, as mentioned above, the form of 



layer between lower surface of 

 a "triangle" and lamellae 



"triangle" 



"line" 



between two 



triangles 



homogeneous 

 pa rt 



fibrillated part 



homogeneous 

 part 



) fibrillated part 



lamellae 



Fig. D. Lactophrys trigonus. Diagrams of plates. 1. seen from above, homo- 

 geneous part not taken into consideration ; 2. vertical section a — a x ; 3. ver- 

 tical section b— b x . The fibrillated part of a plate consists of 1) 6 »tri- 

 angles», in which the bundles of fibres run in horizontal and vertical 

 directions as shown in Fig. E and F, 2) the »lines» or walls between the 

 triangles which continue into a central portion and are connected with 

 each other below by a layer of the same structure, 3) lamellae of bundles 

 of fibres running in different horizontal directions. 



hexagonal plates. Each plate consists of two different por- 

 tions: one superior homogeneous and one inferior, thick and 

 fibrous. The homogeneous portion forms a thin stratum 

 covered with a number of small tubercles of quite the same 

 structure. Some tubercles seem to pierce the epidermis, but 

 their truncate tips scarcely project above the surface of the 

 epidermis. I am not quite sure, whether this is the case 

 always. Some tubercles do not seem to pierce the epider- 

 mis at all. It is possible, that the tubercles in the latter 

 case are not yet fully developed, but it is also possible that 

 this is the natural state, their piercing of the epidermis be- 

 ing caused by insufficient preservation. It is, however, quite 

 certain, that the corium forms a papilla in the epidermis for 



