284 REPORTS ON INVESTIGATIONS AND PROJECTS^ 



at that remote period, such as the nature of their food, their mode 

 of swimming freely in shallow waters, or of crawling about in great 

 schools on the sandy bottom ; the relation of their migrations to tidal 

 currents, as indicated by the constant correspondence between their 

 positions and the axes of the ripple-marks and the position of the 

 stems of accompanying plants. 



The structural features discovered that are new to science and are 

 of special importance or of general interest are as follows : 



(i) The jaws, heretofore supposed to be absent, consist of four 

 separate plates, of peculiar shape, held in place by membranes only, 

 and in life, as their structure clearly shows, acting against each other 

 laterally like the jaws of an arthropod, not forward and backward 

 in the typical vertebrate fashion. 



(2) The location of the olfactory pits on the dorsal side, within the 

 large openings containing the eyes. 



(3) The presence of three pineal (or ocellar) eye-pits. 



(4) The shape and arrangement of the plates and membraues cov- 

 ering the stalked lateral eyes, and the method of raising and lowering 

 the eyes during life. 



(5) The presence of broad, membranous folds, of unknown func- 

 tion, around the posterior end of the cephalic buckler. 



(6) The presence of a very .slender, naked trunk and tail, with two 

 dorsal fins, lateral folds, and a terminal fin, all of an unusual structure. 



(7) The structure and relations of some of the internal organs it 

 is now certain can be determined with some degree of accuracy, such 

 as (a) the shape and location of the mouth ; (6) the shape of the brain 

 chamber ; (c) the presence of a relatively small body suspended by 

 tough connective tissue from the median dorsal wall of the buckler 

 and hanging freely into (d) a large peri-branchial chamber ; (/) the 

 presence of seven pairs of broad lamellae, representing, in whole or 

 in part, the gills ; (g) the exact location of the rectum, anus, and 

 abdominal pores, with accompanying plate-like scales. 



Preliminary papers describing some of the above facts were read 

 before the American Society of Paleontologists and the American 

 Society of Morphologists, at Philadelphia, in December, 1904, and 

 some of the specimens were exhibited there at that time. These 

 papers were based partly on specimens obtained in an earlier explo- 

 ration and in part on those obtained by the grant from the Carnegie 

 Institution of Washington. 



The work now in progress consists of the preparation of photo- 

 graphs, drawings, models of the external form, and the preparation 

 of thin, polished, serial sections of the whole animal to display the 

 structure of the internal organs. 



