Pallial suture and no siphons; freshwater; larva a glochidium.
G, So-called facial "suture" (not really a suture).
P, placenta; o, ovules; s, suture, or median line of carpel.
That any partial fusion of originally distinct chitinous plates takes place in the cephalic shield of Trilobites, comparable to the partial fusion of bony pieces by suture in Vertebrata, is a suggestion contrary to fact.
No ectopterygoid pterygoid not extending to quadrate; no supratemporal or squamosal; prefrontal forming a suture with nasal; coronoid present; vestiges of pelvis present.