
CORRESPONDENCE. 
To the Editor of the American Naturalist : 
Sin: In his article in the May Naturalist on the “ Structure and 
Classification of the Tremataspidzs," Dr. William Patten returns again 
to the question of the origin of the vertebrates from a supposed 
arthropod ancestor. It will be remembered that in two earlier 
papers! he compared the sutures and other markings on the head 
shield of trilobites with those on the dermal armor of Pterichthys and 
Bothriolepis ; and we are confident that paleontologists will dissent 
as strongly from his latest as they did from his earlier conclusions 
that ostracoderms and arthropods are genetically related. The 
view expressed by him about eight years ago, that the three-layered 
dermal skeleton of ostracoderms is a modification of that in arthro- 
pods similar to Limulus, also lacks confirmation from other sources. 
His present procedure, however, is of the boldest; for on the start- 
ling assumption that ostracoderms were animals having many pairs 
of jointed appendages, — on merely a suspicion that this was true, — 
he finds it necessary to “create for them a new class, one that shall 
occupy a position between the true vertebrates and arthropods, and 
unite these two great groups into one compact phylum." ; 
His account of the habits, development, and even some of the 
morphological characters of these * arthropod-like animals" is of 
such extremely speculative nature that few can hope to read with 
him the unwritten records of the past. For if it be not by intui- 
tion, how else can one know that ostracoderms originally progressed 
*through the soft mud on the bottom of shallow water with the 
usual position of dorsal and ventral sides reversed” ; that after leav- 
ing the bottom they righted themselves into the true vertebrate posi- 
tion; and that this acrobatic performance was accompanied by a 
migration of the eyes from the haemal to the neural surface of 
the body? Or in what antediluvian aquarium, we wonder, was 
the locomotion of Eurypterus observed to be “by brief, spasmodic 
excursions"? And what authority have we for supposing that the 
“ hypostomeal eyes of trilobites” (Lindström) were in the slightest 
! Quart. Journ. Mier. Sci., vol. xxxi (1890), pp- 3597365; Anat. Anzeiger, vol. ix 
(1894), pp- 429-438. 
505 
