THE ROTIFERA OF THE SCOTTISH LOCHS. 175 
hexodonta of BERGENDAL, I retain the latter’s specific name in the meantime. Very 
common in bog-pools, casual in lakes ; rarely seen to feed. On one occasion when many 
were found readily feeding, some details of the head were got (fig. 13). The corona is 
fairly large for a pellet-maker, rather less than the collar but greater than the neck in 
diameter. The discs stand some distance apart, and the space between is occupied by a 
conical ligule. The ligule in Bdelloids is of very uncertain stability, often appearing as 
a sport in species where no ligule is normally present, and is therefore an unsafe 
specific character. All the examples of C. hexodonta examined possessed one. The 
very long antenna is kept out when feeding. 
C. pusilla, Bryce (6). (Plate III. figs. 12@ to 12c.) 
The type of this species, having a meagre case, has rarely occurred in our 
collections. The var. textrix is frequent. This has a very bulky case, composed of 
many concentric layers of gelatinous matter. I find two forms which make such 
cases, and consider them as specifically distinct. One, with a very prominent spout- 
like lower lip, is here figured (figs. 12@ to 12c). The other, in which the lower lip is 
not at all prominent, has not been fully studied. The form figured has very prominent 
rostral lamellz, a short, thick antenna with very long set, and the upper lip terminat- 
ing in the median line in a projecting ligule-like process. It readily leaves its case and 
ewanders for some time unprotected. 
C. longiceps, n. sp. (Plate III. figs. 11a to 11e). 
Specific characters.—Small, with oval trunk, longitudinally plicate ; neck narrow, 
of moderate length ; head much elongated ; corona slightly wider than the collar, upper 
lip very extensive; basal segment of rostrum greatly laterally compressed, terminal 
segment fairly long, terminating when fully extended in a very low cone (the everted 
tip) covered with short cilia and with no trace of rostral lamellz. Antenna equal to half 
the diameter of the neck. Teeth 5/5. Food moulded into pellets. Flame-cells spindle- 
shaped ; three pairs seen. Inhabits a firm, membranous, dirty-yellow case, to which 
much extraneous matter adheres. 
Many Bdelloids inhabit houses of some sort for protection. In Rotufer macroceros 
and some other species the house is little more than an untidy accumulation of débris, 
collected by the discs in the process of feeding. Others secrete firm membranous cases 
from the skin of the trunk, and these have a definite form determined by that of the 
body. Others, again, adopt the cast-off shells of other animals, or joints of the limbs 
of arthropods, or even vegetable structures. Callidina annulata, C. scarlatina, and 
the other so-called symbiotic species adopt a ready-made shelter. Cases of definite form 
are most commonly secreted by Callidine of the pellet-making section—among others, 
by C. eremita, C. angusticollis, and C. pusilla, var. textriz. To which class the present 
TRANS. ROY. SOC. EDIN., VOL. XLV. PART I. (NO. 7). 24 
