Profesor Eaton, in his Geological Text-Book, has created a 

 genus of Trilobites, to which he applies the name Brongniartia } 

 comprising B. isotela, (Isotelus gigas. De Kay.) B. carcinodea, 

 fTriarthus Beckii. Green. ) and B. platicephala, (Asaphua platy- 

 cephalus. Stokes.) Dr. Green in his Monograph of Trilobites, 

 has justly thought proper to retain the genus of Dr. De Kay. His 

 second species is the head of either an Asaphus or Paradoxide oi 

 Brongniart, and was previously described by Green, leaving the 

 A. Platycephalus, which is well known to come under the genus 

 Isotelus. The name of Brongniartia then, being unoccupied, I 

 have employed it for this interesting animal, in honor of Professor 

 Alexander Brongniart, not only for the eminence he has attained 

 in science, but in consideration of his having been the first indi- 

 vidual that ever attempted a systematic arrangement of the tri- 

 lobites ; and trilohitoides, from its resemblance both in form and 



EXPLANATION OF THE PLATES. 



Figure L Superior view of the animal, natural size 

 Inferior, do do do 



Platk II. 



1. Head deprived of appendages. 



2. A transverse section, through the first articulation 



after the head. 



3. Mandible with the Palpus. 



4. Maxillae, a. superior, b. inferior. 



5. Tongue. 



6. Labium. 



7. Branchial appendages.* 

 a Paradoxus Boltoni. 



' From 3 to 7. enlarged. 



