especially Cape Hatteras, project onto the shelf 

 and divert water masses. The soutliwestei-ly flow- 

 ing Vii-ginian Coastal Current brings cool water 

 from Cape Cod to Cape Hatteras before it is 

 shunted seuward, and the warm Florida Current 

 flows northeasterly and overlaps the outer edge 

 of the shelf to a point well north of Cape Hatteras. 

 The Carolinian Coastal Current, vaiying greatly 

 in intensity depending on wind regimes, flows 

 southwesterly from Cape Hatteras. The width of 

 the shelf varies from less than 32 km. off Cape 

 Hatteras to more than 80 km. across Onslow Bay. 

 As shown by Cerame- Vivas and Gray (1966), 

 boreal animals from the north and subtropical 

 species from the south are both able to maintain 

 themselves in North Carolina waters. This does 

 not imply that the Continental Shelf of North 

 Carolina is necessarily a transition zone between 

 northern and southern species, but rather that 

 species wnth different geographic affinities may oc- 

 cur in ecologically different areas in North Caro- 

 lina waters, even at the same latitude. 



Three marine biotic areas (fig. 1) have been rec- 

 ognized on the North Carolina Continental Shelf 

 (Cerame- Vivas and Gray, 1966) ; 



A. The Virginian Province is a cold-water, 

 wedge-shaped area that has its apex at Cape 

 Hatteras and widens to the width of the shelf 

 near the latitude of Oregon Inlet. Tliis re- 

 gion is heavily influenced by the Virginian 

 Coastal Current. 



B. The Carolinian Province extends southward 

 from Cape Hatteras and occupies the inner 

 two-thirds to three-fourths of the shelf. In 

 addition to its own fauna, this area receives 

 contributions from the Virginian Province 

 in winter and from the Caribbean Province 

 in summer. 



C. An extension of the Caribbean Province 

 forms the outboundaries of both the Caro- 

 linian and Virginian Provinces and consti- 

 tutes the outer shelf under the Florida Cur- 

 rent. Northward it extends to the point 

 where the Florida Current leaves the shelf. 

 Because of the meanderings of the Florida 

 Current over tlie edge of the shelf under dif- 

 ferent wind regimes (Bumpus, 1955; Bum- 

 pus and Pierce, 1955; Gray and Cerame- 

 Vivas, 1963), neither the northern nor west- 

 ern Ibnits of the Caribbean Province can be 

 precisely defined. 



The boundary between Virginian and Carib- 

 bean Provinces forms a much more formidable 

 barrier to distribution than the barrier between 

 Carolinian and Caribbean Provinces, which in 

 summer is rather diffuse. The "Hatteras Barrier" 

 between the Virginian and Carolinian Provinces is 

 frequently broken in winter when persistent north- 

 east winds (the prevailing winter winds) push 

 Virginian coastal watei-s past Cape Hatteras and 

 Diamond Shoals into Raleigh Bay and beyond 

 (Bumpus and Pierce, 1955; Wells and Gray, 

 1960; Gray and Cerame- Vivas, 1963), creating fa- 

 vorable conditions for "northern" sj^ecies to live 

 in the Carolinian Province temjDorarily. 



ABUNDANCE AND DISTRIBUTION 



Although level bottoms of sand and mud pre- 

 dominate on the North Carolina shelf, scattered 

 here and there are hard substrates : reefs of Trent 

 Marl covered with calcareous tubes of mollusks, 

 coquina formations, encrusted Lithotliamnion al- 

 gae, patches of coral, shelly areas, and wrecks 

 that support a varied and abundant biota. The 

 submerged reefs are well known to fishermen but, 

 unfortunately, have been little studied by biolo- 

 gists. Pearse and Williams (1951) pioneered in 

 describing the biota of the reefs off New River In- 

 let. More recently Menzies, Pilkey, Blackwelder, 

 Dexter, Huling, and McCloskey (1966) made a 

 comprehensive study of a Lifhothamnion reef near 

 the edge of the shelf off Onslow Bay. The fauna 

 listed was predominantly tropical and subtropical. 

 Pearse and Williams reported four .sea-stars on 

 their inshore reefs; Menzies et al. (1966) identified 

 but one asteroid from their offshore reef. Granite 

 substrates are limited to the inshore, shallow-water 

 man-made jetties. Not all sea-stars require a hard 

 substrate, but some that do {Echinaster spinulo- 

 sti-s and Thyraster serpentarius^ for example) are 

 not abundant elsewhere. Grass beds (principally 

 eelgrass Zostera and widgeon grass Rupp/a), 

 limited to soft bottoms of the estuaries, may be 

 ignored as habitats for starfishes, although occa- 

 sionally the very young of Anfej'ia.s forhesii are 

 found here. 



The 33 species of sea-stars defuiitely kiiown to 

 occur on the North Carolina Continental Shelf 

 fall into 22 genera. Of the four genera that have 



SBA-STARS OF NORTH C.\BOLINA 



129 



