[29] ENTOZOA OF MARINE FISHES OF NEW ENGLAND. 481 
The following measurements of head and neck give proportions which 
hold good for all: 







. . Marginal| Lateral 
Dimensions. Sean eae 
| mm. mm. 
ren M PT OTMNOA Cet cle aiciot cm eicin aca daen sae vcecccenssaa=saeacas 0 cnnan = Snsaarcieaseses—~ | 0.90 | 1. 04 
MEH E Rees tesa ce eee eect cctimesieadtaen descent se cde sauecaturaneneeatees 1.10 | 1. 04 
vachcie Te Ge) See oe eee AS Se ARAB pose SSO SCS SSB RSOOCS Se AS OCsSC HOSEISce Or Soepeeda sic 0.76 | 0. 70 
SET O OK TAN TOMO. accccc cciciae semeiasiscs's ce aeine tee sce esos sss secede sdeecee 0. 72 | 0. 76 
EP EEnE UBC K, HOSDOTION. cate aoe wae cccan a ccan s<ecdelneeaciasens--0sse=s=/e=—ns'e 0. 40 | 0. 44 
Breadth of strobile back of neck ........-.-.-- or Or oonaesconnosegnocuntancabeoees 0. 28 | 0. 28 
Millimeters. 
PEEIME TPSN ACIS So. 5 aie cise iclus Da inlcia.tin aise de ccens ca ceamimnwann emote 0. 840 
Breadth of proboscis, exclusive of projecting hooks....-.....---.---.---.---- 0. 043 
Breadth of proboscis, inclusive of projecting hooks .........----.---..------- 0. 078 
PES P AIRLOLININOOKA 2c ispo ao iste esac cision mceiatieieinscnlciemaumaueacavenee se pae 0. 023 
Breminmmofmepaseomanbverlor HOOKS... .<.-ce sse=csacis<cnne wes eloeeseiaacee cane 0.013 
Beeenteot hooks on base of proboscis... -..-.2. 22-2. s0cnseces suseieas os 0014 
Breadth of base of hooks on base of proboscis.......----.------------ See ae 0. O11 
In the summer of 1884 I obtained two lots of these worms from the 
alimentary tract of the Dusky Shark (Carcharias obscurus). 
The first lot, containing approximately 200 individuals, was lodged 
in the pyloric portion of the stomach, where the worms were so massed 
together as to make a swelling in the pylorus which was discernible 
before opening. 
These specimens were not studied closely while they were alive. 
Upon examining them subsequently as alcoholic specimens, it was 
found that there was a very considerable variation in the length of the 
strobiles, and to some extent in the proportions of the segments. In 
the foregoing description I have enumerated those characters which 
belong to all; but inasmuch as there are some more or less clearly 
marked groups among them I shall add some further observations. I 
deem this of importance, for the reason that, if it were not for the 
great number of intermediate forms which these two lots furnish, one 
might be justified in making two, if not three, distinct species instead 
of one. The second lot came from the pylorus and spiral intestine of 
the same species of shark (C. obscurus). 
Three groups were observed in the first lot. These differ from each 
othér principally in the shape and proportions of the segments, the 
distance from the head at which mature proglottides occur, and in the 
total length of the strobile. 
In the first group, which, for the sake of clearness, I shall name var. @ 
(Plate LV, Figs. 9-12), the mature proglottides are flat and thin, square, 
or the posterior ones a little broader than long. When there are but 
few mature proglottides they increase in breadth rather abruptly, so 
that the strobile has a somewhat club-shaped or linear-obovate out- 
line. 
S. Mis. 90——31 
