NO. 9 A NEW ORDER OF CRUSTACEA — PENNAK AND ZINN 5 



large and flat; posterior end, between bases of maxillipeds, forming 

 a broad, smooth semicircle at its extremity. First maxillae uniramous, 

 elongate, and composed of seven segments. Second maxillae uniram- 

 ous, elongate, and 6-segmented ; segments not so broad as those of first 

 maxillae. Postcephalosome appendages (maxillipeds) irregular, flat, 

 and broad ; not distinctly divisible into exopod and endopod. Each 

 thoracic appendage reduced to a small, simple, unsegmented lamella 

 bearing a few terminal setae. Each caudal ramus prominent and 

 curved dorsally to form a large terminal claw. 

 Genotype. — Dcrocheilocaris typiciis. 



DEROCHEILOCARIS TYPICUS, new species 

 Plates i and 2 



Head about one-third as long as the rest of the body and separated 

 from postcephalosome by a* ventral constriction. Head and post- 

 cephalosome distinctly narrower than rest of body. Thoracic and 

 abdominal segments all about the same size. Rostral plate separated 

 from cephalic shield by a well-defined groove, and with three promi- 

 nent notches at its anterior edge. The median notch is deep and 

 ovoid. The lateroventral notches are also deep but are more nearly 

 circular and are toothed along the ventral margins ; it is possible 

 that these may be remnants of chitinous troughs. Near the posterior 

 margin of the median notch are several eyespots. Their number and 

 exact position are variable but typically there are two pairs, one of 

 which is rather small and close to the median line at the posterior 

 end of the notch, while the other two ocelli are larger and more 

 anterior and lateral. The last segment has a prominent median 

 dorsal papilla which bears a single seta and a minute toothed papillule. 

 On each side of the dorsal papilla there is a broadly triangular, flat, 

 short, spinous process. The two caudal rami are slightly longer than 

 the last segment, broad at the base, and are curved dorsally in the 

 form of a large claw. Each ramus bears three large plumose setae, 

 one dorsal and two lateral. The two lateral setae originate at about 

 midlength of the ramus, one being slightly shorter than the ramus 

 and the other about twice as long as the ramus. The dorsal seta 

 originates near the base of the ramus and is slightly longer than the 

 ramus. There are two small papillae on the dorsal surface of each 

 ramus, the anterior one bearing a fine seta. Along the median ventral 

 edge of each ramus are three small equidistant processes each of 

 which bears a spinule. 



The lateral chitinous troughs of the head are situated near the 

 posterior margin of the cephalic shield; each of these is roughly 



