360 The American (ieoloyist. June, 1893 
Thus far and no farther at present the placoderms in this 
peculiar form have been traced down from layer to layer in 
the stratified crust and from region to region to the place 
above mentioned. At the same time their structure has be- 
come more and more simple and their size smaller until at last 
we seem to have caught them almost at the moment of origin- 
ation. Hut this may not be so, and in strata yet lower we 
may some day find ancestors more ancestral, placoderms less 
placodermic. lishes less fish-like than even these strange and 
almost primeval efforts of Nature's hands and skill. 
ON THE VALIDITY OF THE FAMILY BOHEMILL- 
ID/E, BARRANDE. 
By C. E. Beecheb, New Haven, Conn. 
In the supplementary volume on the trilobites of Bohemia, 
published in 1872, Barrande carefully figures and describes 
two imperfect specimens of a trilobite which apparently differs 
widely from all known genera. For this species he proposes 
the name Bohemilla st.upenda, which expresses the importance 
and remarkable characters it was believed to possess. On 
account of the impossibility of referring it to any existing 
group, the family Bohemillidoi was constituted for its recep- 
tion. 
During the past two years, the writer has had occasion to 
review all the families and genera of trilobites, and the 
Bohemillidoi was the only one which could not be readily in- 
terpreted in terms of known trilobite morphology. Barrande's 
figure of the principal specimen of B. stupenda* showed a fur- 
row on the curved base of the so-called genal spine which was 
very suggestive of a pleural groove, and the finely striated 
spine itself resembled a doublure. Moreover, as there were no 
defined pleura on the thorax, the specimen seemed to represent 
only the axis of an ordinary trilobite. The second specimen 
figured, being simply the glabella, is of no value in this dis- 
cussion. 
Through the courtesy of Prof. Agassiz and Dr. K. T. Jack- 
son, a study was made of the t} r pes of this species, now in the 
Museum of Comparative Zoology at Cambridge. This investi- 
gation showed that the foregoing surmises were correct, and 
*Syst. Sil. tin centre de la Boheme. vol. f , Suppl., pi. 14, figs. 30-32. 
