THE EURYPTERIDA OF NEW YORK 407 
The description of the branchiae will be found under the description 
of Sidneyia, the typical genus of the Limulava. 
Observations. The suborder Limulava differs from the Eurypterida, 
to which it is most nearly related, in having a large epistoma similar to 
that of the Trilobita; in not having a metastoma, chelate antennae, and 
swimming cephalic appendages; and in having a broad, fan-shaped caudal 
fin, and branchial appendages more or less unlike the lamellar branchiae 
of the Eurypterida and Xuiphosura. 
The relations of the order and suborder are shown in the following 
tabular view: 
Subclass MEROSTOMATA 
Order Eurypterida Suborder Limulava 
1 Cephalothorax long 1 Cephalothorax short 
2 Cephalothorax with six (6) pairsof 2 Cephalothorax with five (5) pairs . 
appendages; the anterior pair — of appendages; the anterior 
chelate antennae, and the poste- simple antennae, the third pair 
rior pair, long, strong swimming multichelate, and the posterior 
legs pair short, the outer joint serv- 
ing as a branchial organ 
3 Epistoma present in Pterygotus 3 Epistoma large. Metastoma un- 
where it is narrow. Metastoma known 
large 
4 Six anterior abdominal segments ~4 Nine anterior abdominal segments 
bear leaflike branchial appen- bear leaflike branchial appen- 
dages dages 
s Surface of test with scalelike orna- 5 Surface of test smooth or with im- 
mentation bricating lines, as in many of 
the Trilobita 
Terminal segment a simple lanceo- 6 Terminal segment a caudal fin 
late or spatulate telson formed of a central expanded 
telson and one or more swim- 
merets on each side 
Ov 
In view of the unusual structures here set forth it is germane to this 
work to inquire whether these Limulava should be construed as belonging 
to the Eurypterida in the capacity of a suborder or if they may not more 
properly assume a higher grade as an independent and coordinate group. 
_ The Eurypterida, as represented by the genera hitherto referred to 
them, constitute a very compact order with well fixed characters. If 
