FISHERY BULLETIN: VOL. 86, NO. 2 



3rd 

 4th 

 5th 



ischio- 

 merus 



6.14 

 5.76 

 5.44 



carpus propodus 



2.56 

 2.18 

 2.30 



3.78 

 4.12 

 5.44 



dactyl 



0.64 

 0.70 

 0.64 



Each short dactyl armed with 5 spines on flexor 

 surface, grading from small proximally to longest 

 and strongest distally, often a sensory seta on 

 extensor surface. Propodi with setae along flexor 

 surface progressively more crowded distally. 

 Carpi with distodorsal extension projecting as a 

 stop along proximal part of propodal extensor sur- 

 face. Third leg stronger, at least in merus- 

 ischium, than fourth and fifth; merus of third and 

 fourth with closely appressed ventral spine at 1/2 

 and 3/4 length, that of fifth with spines at 1/3 and 

 2/3 length, distal spine strongest in each case; 

 ischium of third and fourth leg with 2 spines in 

 line with those on merus. 



Pleopods well developed, pair 1 with endopods 

 about half length of exopods, tapering to acute 

 tip; appendices internae simple, that of pair 5 

 with blunt tip. 



Uropod (Fig. Id) with rami subequal in length, 

 slightly exceeding distal end of telson, lateral 

 ramus with movable spine mesial to smaller dis- 

 tolateral tooth, diaeresis sinuous. 



Remarks. — Remarks are given in the account 

 for A. stactophila. 



Etymology. — The name is taken from an 

 acronym for the site of collection in the Mid- 

 Atlantic Ridge Valley about 70 km south of an 

 area known as the Kane Fracture Zone, "MARK", 

 and the Latin genitive suffix "ensis". 



Alvinocaris muricola new species 



Figures 3, 4, 7 



Material .—\JSnU 234288, Holotype c^ (ceph- 

 alothorax and abdomen broken apart), USNM 

 234289, Allotype 9, West Florida Escarpment, 

 26°01'N, 84°54.61'W, 3,277 m, Alvin Dive 1754, 

 15 October 1986, pilot W. Sellers, observers 

 R. Carney and B. Hecker. USNM 234290, Para- 

 type 9 , West Florida Escarpment, same locality, 

 Alvin Dive 1753, 14 October 1986, pilot P. Tib- 

 betts, observers R. Carney and G. Knauer. All 

 from Barbara Hecker, Lamont Geological Ob- 

 servatory, Columbia University, Palisades, NY. 



Measurements in mm. — Holotype 6, postor- 

 bital carapace length 6.4, rostrum 4.4, maximum 

 carapace height 4.5. Allotype 9 , same, 6.4, ros- 

 trum broken, 5.6. 



Description. — Integument thin, shining, mi- 

 nutely punctate. Rostrum (Fig. 3a, b) almost 

 straight to slightly upturned in distal half, 

 sharply pointed tip reaching to proximal part of 

 third peduncular article of antennule; dorsal mar- 

 gin raised into thin serrate crest containing 17-21 

 teeth varying from obliquely erect in proximal 

 part to nearly horizontal, shorter and more dis- 

 tant distally, about 1/3 length of crest continued 

 onto carapace; ventral margin much less promi- 

 nent and armed with row of 6 correspondingly 

 smaller subterminal teeth, sometimes obscure; 

 lateral carina broadened proximally and conflu- 

 ent with orbital margin. Carapace (Fig. 3a ) with 

 broad based but slender, acuminate antennal 

 spine; pterygostomian spine correspondingly 

 acuminate and prominent. Prominent anterior 

 antennal carina curving posteroventrally to in- 

 tersect obliquely with carina extending from 

 pterygostomian spine at about midlength of cara- 

 pace, associated groove continuing indistinctly 

 posteriad. 



Abdomen (Fig. 3d,e,f) of both male and female 

 broadly arched dorsally, gradually tapering dis- 

 tally, narrowest part of sixth somite less than 2/3 

 (0.60) width of first somite; pleura of 3 anterior 

 somites broadly rounded, margin of third slightly 

 serrated, that of fourth somite drawn posterolat- 

 erally to strong spine flanked dorsally by 0-3 

 more slender and smaller spines and preceded on 

 ventral margin by 0-2 small spines; number, po- 

 sition, and shape of either lateral or ventral 

 spines may be asymmetrical; posterolateral cor- 

 ner of fifth pleura acuminate and flanked dorsally 

 by 1 or 2 spines analogous to those on somite 4; 

 sixth somite with middorsal length about 1.7 that 

 of fifth, broad-based midlateral spine overlapping 

 base of telson, smaller posterolateral spine acute; 

 fourth and fifth somites each with strong, posteri- 

 orly directed spine on sternite. Telson (Fig. 3^) 

 elongate subrectangular, length about 3.0 ante- 

 rior width, 6.8 posterior width, and about 1.4 

 length of sixth somite, not including posterior 

 spines; armed with 7 dorsolateral spines of nearly 

 uniform size; posterior margin convex, armed 

 with 2 principal spines at each corner and 10 or 11 

 feathered strong setae on distal margin between. 



Eyes (Fig. 3a, b) with cornea imperfectly devel- 

 oped, unfaceted though diffusely pigmented. 



268 



