204 Cincinnatt Society of Natural History. 
ing from the symmetry of the matrices of the Meropodites, as well as 
from the general cylindrical character of limbs themselves, 
On the ventral surface of the pygidium there are at least twelve 
(pairs of) appendages; posteriorly, an exact enumeration is impossible. 
The term pazrs is used on account of the median groove, showing in 
the structures a bilobed character. This groove is continuous with 
the thoracic groove, and is somewhat narrower and more shallow than 
the latter. From an examination of the two specimens, these twelve 
or more appendages appear to be leaf-like, or foliaceous, and on each 
side of the median groove the direction was outward and somewhat 
forward. No doubt these appendages were branchial in function, and 
also adapted to swimming. 
These specimens will prove of interest to zoologists, especially from 
a taxonomic point of view. Spence Bate and Henry Woodward, of 
England, and Prof. Dana, of this country, regard the Trilobites as 
closely related to Isopoda. Woodward homologizes thus: 
TRILOBITA (fossil or extinct). 
1. Eves sessile, compound. 
2. No ocelli visible. 
3. Appendages partly oral, partly am- 
bulatory, arranged in pairs. 
4. Thoracic segments variable in num- 
ber, from six to twenty-four, free, mov- 
able; animal sometimes rolling in a ball. 
5. Abdominal somites coalesced, form- 
ing a broad caudal shield, bearing the 
branchiz beneath ? 
6. Lip-plate well developed. 
IsopopA (fossil and living). 
1. Eyes sessile, compound. 
2. No ocelli visible. 
3. Appendages partly oral, partly am- 
bulatory, arranged in pairs. 
4, Thoracic segments variable in num- 
ber, from six to twenty-four, free, mov- 
able; animal sometimes rolling in a ball. 
5. Abdominal somites coalesced, form- 
ing a broad caudal shield, bearing the 
branchie beneath. 
6. Lip-plate small. 
If the conclusions herein expressed in the interpretation of the 
abdominal appendages of Asaphus megistos are correct, then the mark 
of doubt in No. 5 of Woodward’s homological table may be removed. 
Prof. E. Van Beneden, of Belgium, believes the Limuli are not crus- 
taceans, and, from a study of their embryology, concludes that they 
can not be separated from scorpions and other arachnida. This view, 
in which he is not alone, if correct, would carry the Trilobites out of 
the class crustacea. 
Dr. Packard, in his excellent work on the ‘“ Development of Limulus 
polyphemus,” places the Xiphosura and Eurypterida as suborders under 
the order Merostromata, which is followed by Trilobita as a separate 
order. This view is accepted by Dr. Lockwood and Mr. C. D. Walcott. 
It remains for zoologists to place whatever value may attach to the 
fact of the appendages of Trilobites subserving the purposes of bran- 
chial organ, of manducation, and of locomotion, either ambulatory or 
natatory. 
