March, 2000 
SCAMIT Newsletter 
Vol. 18, No. 11 
separate the two species; they are very 
proximal in M. major , and removed from the 
base of the telson in F. obtusidens. Other 
characters of potential interest are the rostrum, 
the relative widths of the 4th and 5th articles of 
P5, the shape and posterior setation of pleonal 
epimera 2 and 3, the relative width of the 
second article of the mandibular palp, and a 
series of others listed by Barnard 1960, 
Barnard & Barnard 1982, and Jarrett & 
Bousfield 1994. Of these the easiest to see is 
the rostrum length, but it takes direct 
comparison of the two taxa and a little eye 
training to be able to separate them on only that 
basis. [This character, by the way, is evident 
even in fairly small juveniles of M. major 
based on the editor’s experience.] 
Dean brought a cumacean specimen he was 
calling Leucon sp. H, now known as Leucon 
declivis (Watling & McCann 1997). We 
examined the specimen and concluded that it 
was actually a Leucon magnadentata Given 
1961 based on carapace and uropod details. 
Dean reached that ID using the earlier key of 
Cadien (a 1986 SCAMIT meeting handout). 
Both species are normally found in much 
deeper water than was Dean’s specimen, but 
both have a few shallower records, and the type 
of L. magnadentata came from only slightly 
deeper than the animal at hand. Neither species 
is currently on the SCAMIT list, so this animal 
represents a nice addition. 
Dot Norris (CCSF) brought several interesting 
species from the Bay area for examination.The 
first was an ampeliscid from near the mouth of 
San Francisco Bay which was either Ampelisca 
abdita or the very similar A. milleri. The 
introduced A. abdita is the dominant 
ampeliscid species in the Bay, but the specimen 
examined turned out to be A. milleri based on 
the criteria used by Chapman (1988) to 
separate the two. Most persuasive was the 
shape of the dactyl and relative proportions of 
articles 4, 5, & 6 on P6. 
She brought along a small Photis to confirm 
that it was P. macinerneyi, and it was. Dean 
provided her with a copy of his Photis key, 
which she did not have. She also brought down 
specimens of Synidotea believed to be S. 
laevidorsalis . These were examined by Tim 
Stebbins (CSDMWWD) who has been working 
with the group. We quote below from his e- 
mail on the subject: 
“I looked at your Synidotea specimens, 
mostly just at the larger one for the 
moment. I believe what you have is 
Synidotea consolidata Stimpson, 1856. 
This would correspond to S. bicuspida in 
Menzies and Miller’s (1972) account of 
the California Synidotea , as well as in the 
isopod chapter of Light’s Manual (Miller, 
1975). Rafi and Laubitz (1990) discuss 
briefly the distribution of these two 
species, the end point being that S. 
consolidata is the beast ranging into your 
area, while S. bicuspida is now 
considered restricted to arctic waters. I 
talked to Rick [Brusca] and he is in 
agreement with this, thus this is what 
should be coming out in the new Light’s 
Manual (whenever that is). 
Briefly, your critters do have some body 
sculpturing, although it’s reduced to a 
few small tubercles or horns on the 
cephalon and transverse carinae (ridges) 
on the pereonites. These characters would 
eliminate the “smooth” bodied S. 
laticauda and S. harfordi. Synidotea 
laticauda is also pretty much restricted to 
estuarine habitats instead of the offshore 
environs where you found these beasts. A 
definitive character for S. consolidata is 
the morphology of the appendix 
masculinum (a.m.) in males: curved near 
the apex and densely spinulose. Your 
larger specimen is a male and I could see 
the “curved” aspect of the a.m. clearly, 
although I would need to remove it to get 
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