302 FRED J. PACK 



Fig. 2. — Zacanthoides iypicalis, Walcott. 



2. View of specimen closely resembling the type; twice natural size. Collection 



Columbia University Museum, No. 20024. 



20. View of head showing the postero-lateral limbs attached; twice natural size. 

 Collection Columbia University Museum, No. 20025. 



2b. Specimen showing remarkably long genal spines, long spines on postero- 

 lateral limbs, but, so far as revealed, no spines on thoracic segments; twice 

 natural size. Collection Columbia University Museum, No. 20026. 



2C. Specimen showing considerable spinosity, twice natural size. Collection 

 Columbia University Museum, No. 20027. 



2d. Specimen with long genal spines, also long spine on the next to the last tho- 

 racic segment; natural size. Collection Columbia University Museum, 

 No. 20028. 



26. Very commonly associated free cheek showing outward flexure toward the 

 end of spine; twice natural size. Collection Columbia University Museum 

 No. 20003. 



2/. Hypostoma associated with this species; natural size. Collection Columbia 

 University Museum, No. 20029. 

 Fig. 3. — Zacatithoides grabaui, n. sp. 



3. Prototype showing the general form of head, triangular frontal margin, and 



nearly straight genal spines; natural size. The free cheek has been slightly 



adjusted. Collection Columbia University Museum, No. 20031. 

 3a. Paratype showing the general nature of the head, also the knob or spine 



on the occipital ring; natural size. Collection Columbia University Museum, 



No. 20031. 

 3&. Cast of paratype showing nature of third pleural lobe and the attached spine, 



natural size. Collection Columbia University Museum, No. 20032. 



