60 GEOL. AND NAT. HIST. SURVEY OF MINNESOTA. 
two larger spines; the inner ramus is of moderate size. The inner ra- 
mus of the outer leg is obsolescent. The accessory spine of the outer 
ramus is near the middle of its segment. Length 1.0 mm. 
Marsh finds this form in Green lake and the Great Lakes; it may, 
therefore, be expected in Lake Superior in Minnesota. 
* Diaptomus ashlandi Marsh. 
PLATE VI, Fias. 4-6. 
Marsh ’93. 
‘‘A small pelagic species closely resembling D. sicilis Forbes. In 
form it is slender, hardly to be distinguished from D. sicilis and D. 
minutus. The first joint of the abdomen in the female is longer than 
the remaining part of the abdomen, is dilated at the sides and bears. 
two minute lateral spines. The second and third joints are so closely 
united that the abdomen appears two-jointed. The -furcal joints are 
about twice as long as broad. The antenn reach just beyond the 
furca. The right antenna of the male is much swollen anterior to the 
geniculating joint, and bears on the antepenultimate an appendage 
Slightly exceeding in length the penultimate joint. This appendage 
may be blunt pointed or slightly enlarged at the extremity. The 
fifth feet of the female are rather slender; the outer ramus is two- 
jointed. The third joint is represented by two short spines. The 
inner ramus is one-jointed, a little longer than the first joint of the 
outer ramus, armed at the tip with two rather long spines. 
““The feet of the male are slender. The basal joint of the right foot 
is about twice as long as that of the left. The first joint of the outer 
ramus is a little wider than long. The second joint is wider at the 
inner than the outer end; the lateral spine is stout, curved, situated 
near the inner end. The terminal hook is slender and falciform. ‘The 
inner ramus is slender, one-jointed, and about one-third longer than 
the first joint of the outer ramus. The left foot extends a little beyond 
the first joint of the outer ramus of the right. The second joint of the 
outer ramus has three blunt spines upon its apex and is armed with 
minute bristles within. The inner ramus is slender, one-jointed, and 
reaches about half the length of the second joint of the outer ramus. 
Length of female 0.97 mm.; of male 0.89 mm,’’ 
This is a pelagic species found in Lake Superior and others of the 
Great Lakes, and consequently occurs upon the shores of Minnesota. 
* Diaptomus sicilis Forbes. 
PLATES V, Frias: 1-73: e011, Pia ds: 
Herrick ’83 and ’34; De Guerne and Richard ’89; Forbes ’91; Marsh ‘93. 
The discrepancies respecting this species as described by various 
authors must be due to heterogenesis. It varies greatly in size and 
armature of the feet. The form is slender and graceful and very like 
