4 . 
THE ECHINODERMS OF THE WOODS HOLE REGION. 565 
Mellita pentapora (Gmelin). Key-hole Urchin. (PI. 10, figs. 63-64.) 
Echinus pentaporus Gmelin, 1788 
Seutella quinquefora Lamarck, 1816. 
Encope pentapora L. Agassiz, 1841. 
Mellita quinquefora L. Agassiz, 1847. 
Mellita testudinaria Gray, 1857. 
Mellita pentapora Liitken, 1864. Verrili, 1873, et set}, 
Mellita tesfudinata Alex. Agassiz, 1872. 
Description.— Test very flat, often wider than long when fully grown, truncated posteriorly, covered 
with very short, delicate spines, which are longest actinally, especially near the margin in the inter- 
radii, around the peristome or bordering the lunules. There are 5 of the latter, 1 in the posterior 
interradius and 1 in each radius, except the anterior one. Ambulacra obvious abactinally as bluntly 
rounded, nearly closed “petals,” not quite reaching the lunules, the posterior pair longer; actinally 
the ambulacra appear as shallow furrows, the anterior running to the margin, the others ending at the 
lunules. Abactinal system eccentric, lying anterior to the center while the mouth is directly below; 
genital pores 4. Anal opening actinal; in adults, at the proximal end of the interradial lunule. 
A good-sized specimen gives the following measurements: Longitudinal diameter 110 mm.; trans, 
verse diameter 115 mm.; vertical diameter 10 mm.; diameter of abactinal system 9 mm.; length of 
anterior petal 32 mm.; length of posterior petal 39 mm.; length of interradial lunule 22 mm.; width of 
interradial lunule 3 mm. ; distance from margin 23 mm.; length of postero-radial lunule 24 mm. ; width 
of postero-radial lunule 2 mm. ; distance from margin 3 mm. 
The difference between the longitudinal and transverse diameters is not always as marked as hi 
the specimen given; moreover, very young specimens have the lunules only partly formed or wanting. 
In a specimen 3 mm. in diameter there are no lunules, but the position of the interradial one is indi- 
cated by a slight actinal depression. A specimen 12 mm. in diameter has the interradial lunule fully 
formed, the deepening of this actinal depression having continued until the abactinal surface was pierced; 
the radial lunules are arising as notches in the edges of the test. These marginal notches deepen, and 
finally the outer sides grow together, thus inclosing the lunule. Color in life, brownish-yellow; in 
alcohol, rather greenish. 
Range. — Nantucket to Brazil, in shallow water; rare and local, north of Cape llatteras. 
Remarks. — This species is admitted to the list of the Woods Hole echinoderms on very scanty 
evidence. Verrili (’73 b) records it from Nantucket on Agassiz’s authority, and dead specimens (bare 
tests) are occasionally taken in Vineyard Sound. Where these come from is a question yet to be 
answered. Mr. Gray tells me one was taken in the sound in the summer of 1901. Dr. Caswell Grave 
(1902) has published a brief and partial account of the larva of this species, and I am indebted to him 
for some of the details of the above description of the adult. 
HOLOTHURIOIDEA. 
HOLOTHURIANS. SEA-CUCUMBERS. 
The holothurians make up more than one-third of the Woods Hole echinoderms, 
but although the number of species is considerable, in number of individuals the 
asteroids and echinoids far outrank them. None of the nine species are sufficiently 
common and generally distributed to be noticed by an inexperienced observer, and it 
is the exception rather than the rule to find a holothurian in the dredge anywhere 
in the Woods Hole region. There are, however, three species {Thymic hriareus and 
the two t Synaptas ), which one who knows where and how to look can always obtain, 
and these we may fairly call common. The remaining six are of uncertain occur- 
rence, and while two of them may lie expected to occur at the proper locality, the 
others are distinctly rare and of uncertain occurrence. I have never seen any of 
these four living. The various species can be distinguished from each other with 
comparative ease, and few of the terms used in the descriptions will need any 
explanation to anyone at all familiar with echi noderm anatomy. The names applied 
