1885.] Progress of N. A. Invertebrate Palaontology for 1884. 353 
the carnivore Proteles, the Pteropod bats, and the aye-aye. Also 
where teeth are lost from the series, as in the canine genus Dyso- 
dus, and in man. The loss of the hallux and pollex without 
corresponding gain, in various genera, may be regarded in the 
same light. 
In conclusion, the progressive may be compared with the 
retrogressive evolution of the Vertebrata, as follows: In the 
earlier periods and with the lower forms, retrogressive evolution 
predominated. In the higher classes progressive evolution has 
predominated. When we consider the history of the first class 
of vertebrates, the Tunicata, in this respect, and compare it with 
that of the last class, the Mammalia, the contrast is very great. 
:0: 
PROGRESS OF NORTH AMERICAN INVERTEBRATE 
PALZZONTOLOGY FOR 1884. 
BY J. B. MARCOU. 
* Sale year that has just passed has been fairly prolific in palæ- 
ontological work, about fifteen more titles appearing in this 
review than there were in the last; it is true that a few of them 
should have been inserted last year, but doubtless some titles 
have escaped me also this year, and the two errors may be con- 
sidered to compensate each other; so that we have an increase of 
about one-third in the number of articles published. There is 
also a general improvement in the quality of illustrations, though 
of course there is still plenty of room for improvement, and it is 
surprising.that some paleontologists should persist in publishing 
a large number of descriptions with no illustrations at all, or with 
such imperfect illustrations as to render them practically useless ; 
the chief result brought about by such publication of species is 
an increase of our already voluminous synonymy. The day will 
_ doubtless come when descriptions of new species unaccompanied 
by proper diagnoses and illustrations will no longer be recog- 
nized, for it is next to impossible to recognize a form from a mea- 
ger description unaccompanied by an illustration. The founding 
of new genera and species on very imperfect specimens is also a 
very reprehensible practice, for although it may be excellent ex- 
ercise for the imagination of the author, yet it may introduce 
errors which it will take a great deal of time and trouble to eradi- 
cate, especially when there is no indication that such descriptions 
VOL. XIX.—NO. Iv. 23 
