WIGLEY and STINTON; REMAINS FROM MARINE SEDIMENTS 



uran (true) crabs. Remains of the latter group 

 consisted of the larger more massive and durable 

 parts of the skeleton (mainly the carapace and 

 chelipeds) , and the anomuran remains consisted 

 only of chelipeds. Occurrence records for both 

 groups of crustaceans are included in Table 19 ; 

 bathymetric data are given in Table 20. The 

 geographic and bathymetric distributions are il- 

 lustrated in Figures 24 and 25. 



Remains of cirripedes (Figure 23 A) were 

 widely scattered over the area (Figure 24) . The 

 density of major fragments ranged from 10 to 

 90/m-; densities were substantially higher in 



shallow water than in deep water. The depth 

 range was 27 to 567 m with the average depth 

 at 123 m. 



Remains of crustaceans carapaces and che- 

 lipeds were from anomuran and brachyuran 

 crabs ( Figure 23B ) . They were sparse to mod- 

 erately dense and had a somewhat limited geo- 

 graphic distribution near the central part of the 

 shelf (Figure 24) at depths from 51 to 113 m. 

 Their distribution was much more restricted 

 than that of cirripedes. Also, this part of the 

 shelf is a low-energy region, as compared with 

 the Nantucket Shoals and the shallow inshore 

 areas where cirriped remains were prevalent. 



Table 19. — Density of crustaceans and coelenterates, 



by station. 



Station 

 number 



Crustaceans 



Coelenterates 



Cirripedes 



Anomuran- 

 brachyuron 



Flabellum Acanellai'i) 



No/nfi 



Nolrrfi 



20 



50 



30 



80 

 10 

 50 



Table 20. — Bathymetric distribution of crustaceans and 

 coelenterates, and the number of stations at which they 

 occurred. 



COELENTERATES 



Coelenterate remains were the rarest group 

 of animals in the prefossil assemblage. They 

 consisted solely of corals: Flabellum alahastrum 

 i=goodei Verrill), a cup coral, and Acanella 

 ( ?) , a bush coral. Some examples of each kind 

 are illustrated in Figure 23. 



Flabellum, a solitary coral of the madrepo- 

 rian group, has a rather large (4 by 6 cm) polyp 

 and a typical calcareous skeleton (corallite) with 

 well-developed septae. Corallite remains con- 

 tained a large proportion of septae and were 

 commonly 4 to 8 mm long. This species occurred 

 only in a limited area on the continental slope 

 south of Martha's Vineyard (Figure 24) at 

 depths of 146 to 366 m (Figure 25). Densities 

 of fragments were as high as 80/m'-, but the 

 average density at the locations where they oc- 

 curred was about 40/m-. 



White calcareous rodlike structures about 

 0.5 mm in diameter and 0.5 to 1 cm in length 

 (Figure 23D) were provisionally classified as 

 Acanella, a colonial alcyonarian coral. The 

 fragments appeared to be internodal portions of 

 the axial skeletons. Acanella normani Verrill 

 is not uncommon in the region. The multi- 

 branched colony of this species is composed of 

 numerous slender, jointed segments. Total 

 height of a full-grown colony is usually less than 

 30 cm. Remains of this coral were found at two 

 stations near the center of the area (Figure 24) 

 at depths of 90 to 97 m and in densities of 20 

 to 50/m^ 



35 



