B20. 1, 1883] 
cannot be numbered. Some other kind of fish are evidently 
the descendants of primordial ‘‘ Marsipobranchs,” notably Zefz- 
dosteus, the development of which has been lately studied, and the 
results are being published in the P%z/osophical Transactions. 
But the Chimeroids, Dipnot, and, still more important, the 
Myxinoids themselves, have still to be followed through their 
early stages. If the present paper is of any value to the 
snorphologist, one on the embryology of these low forms would 
be worth much more. 
The Myxinoids keep on the low ‘‘ platform” of the larval 
Lamprey (Ammocete) in the following particulars, namely :— 
a. The notochord has no paired cartilaginous vertebral rudi- 
ments in the spinal region. 
6. The trabeculze end in the ethnoidal region, without growing 
forwards into a cornu (or wo continuous cornua). 
c. There are merely “‘ barbels”’ round the mouth; no /adial 
cartilages. 
d. The last character involves this, namely, that the special 
armature of horny teeth, attached to the labials in the adult 
Petromuy'zon, is absent. 
é. The organs of vision are very feeble, and probably almost 
useless ; in the 4mmocate they are arrested for a time. 
J. The cranium is a mere /foor, without side-walls or roof. 
The Myxinoids come near to the adult Lamprey in the follow- 
ing particulars, namely :— 
a. There are developed outside the skull proper, but not 
segmented from it, palato-pterygoid and hyoid cartilages. 
6, There is a very large median cartilage belonging to both 
the hyoid and branchial regions. 
¢. The cranium acquires a floor by the development of a 
special ‘‘ hinder intertrabecula.” 
d, There is a large median cartilaginous olfactory capsule. 
The Myxinoids go beyond even the adult Lamprey in the 
following particulars, namely :— 
a. The facial basket-work is much more perfect ; and as ‘his 
is a generalised condition of the true zm/ra-visceral system of 
cartilages, it is a very important character ; there is not only an 
equal development of the ‘‘suspensorium,” but the szspensorial 
part of the hyoid is developed also (it is suppressed in the 
Lamprey) ; and there is, in Bdellostoma a large complete first 
branchial arch, and in both kinds pharyngo-branchial rudiments 
of the second branchial arch. 
6. The respiratory (branchial) pouches are much more spe- 
cialised by being carried far back under the spine. 
c. There is not only a distinct sub-cranial intertrabecula, but 
also a large pre-cranial or nasal median cartilage of the same 
nature. 
d, The opening of the median olfactory sac is not a mere 
short membranous passage, but a long tube, encased in a series 
of cartilaginous (imperfect) rings. 
e. Correlated with the non-development of the suctorial labial 
cartilages, there is an enormous development of the lingual, the 
basal bar becoming not only double, but, in front, quadruple, 
and the ‘‘supra-lingual” cartilages, which are very small in the 
Lamprey, and carry only one pair of rows of small second teeth, 
in the Myxinoids are very large, and carry two pair: of rows of 
large teeth, wlth the addition of a median antagonistic ‘‘eth- 
noidal tooth,” 
Lastly, the greater development of the intra-visceral (= ‘‘ intra- 
branchial”’) cartilages is correlated with the suppression of the 
extra-visceral basket-work seen both in the larval and adult 
Lamprey, and also in the larvee of the ‘‘ Anura” generally. 
) 
January 18.—‘‘On the Skeleton of the Marsipobranch 
Fishes. Part II. The Lamprey.” By W. K. Parker, F.R.S. 
The suctorial mouth has its highest development in the 
Lamprey ; in the Myxinoids (AZyxine), and Bdellostoma, there is 
no circular disk with horny teeth, but merely an oral fissure 
surrounded by barbels, and having inside it a huge tongue beset 
with two oblique rows of recurved and inturned horny teeth, 
antagonised by a single ethnoidal tooth. Inthe larva of the 
Lamprey the mouth is not circular, and the ewer lip is far back, 
covered by the #Aer, which is like a hood; there are no teeth 
of any kind, only moss-like ‘‘barbels” or fZafi//e under the 
upper lip. 
In the Tadpole the mouth is suctorial, the /ower lip being con- 
verted into an imperfect ring, which is completed by the wpjer 
lip. Here the cartilage of the lower lip is not a perfect ring, as 
in the Lamprey, but is in two parts, and is formed into a sort of 
horseshoe, Inside this compound ring there are sharp horny 
NATURE 
331 
plates or teeth, and the folds of the lips, all round the mouth, 
are covered with a horny rasp. 
Correlated with the perfectly suctorial Jowér lip of the 
Lamprey, which, is a fost-oral structure, entirely, we have the 
perfectest form of the superficial branchial skeleton, a basket- 
work of soft cartilage which appears in the early embryo, and 
only gains enlargement fore and aft, and all its snags and out- 
growths, after metamorphosis. Besides this there are no rudi- 
ments of z¢ernal branchial arches, such as we find in the Tad- 
pole. The only parts developed zwside the head-cavities and 
branchial arches are the generalised and rudimentary mandibular 
and hyoid arches. In the Tadpole there is no fier to the hyoid 
arch, and the frst cleft is arrested as a small blind pouch ; this 
state is persistent in the Lamprey. But, after metamorphosis— 
as the lingering latter part of that profound change of structure— 
the young Frog and Toad acquire a pier to their hyoid arch, 
right and left. This, however, does not become functional to 
the arch, much less assist in supporting the mandible, asa ‘‘ hyo- 
mandibular,” but is transformed into an osseo-cartilaginous chain 
—a stapedio-incudal series, specialised correlatively with the 
expanded rudiment of the first cleft, now enlarged into a cavum 
tympani, with a large ‘Eustachian opening.’ The little 
mandibles of the Tadpole, which served as arms to carry the 
divided suctorial disk, and lay across the fore face, become very 
long, and are often hinged on to their pier behind the occiput, 
and the cartilages of the suctorial disk straighten out and add to 
the length of the lower jaw in front. These things show how 
this temporary ‘‘ Petromyzoid,” the Tadpole, blossoms out into 
unthought-of specialisations ; it becomes a guast-reptile, worthy 
of a place far above the Lamprey, and even far above all other 
Ichthyopsida, 
Geological Society, January 10.—J. W. Hulke, F.R.S., 
president in the chair.—T, W. Edgeworth Pavid, the Earl of 
Dysart, John James Hamilton, Francis Alfred Lucas, and 
Meaburn Staniland, were elected Fellows, and Dr. Otto Torell, 
F.C.G.S., of Stockholm, a Foreign Member of the Society.— 
The following communications were read :—On the Lower 
Eocene section between Reculvers and Herne Bay, and some 
modifications in the classification of the Lower London Tertiaries, 
by J. S. Gardner, F.G.S.—The author noticed Prof. Prestwich’s 
classification of the Lower London Tertiaries, and the intro- 
duction by the Survey of the term ‘‘ Oldhaven Beds” for some 
of his basement beds of the London Clay. He next discussed 
the conditions under which the Lower Tertiaries were produced, 
and showed that throughout the Eocenes there are indications of 
the close proximity of land and of the access of fresh water. 
Two types of faunas are to be recognised, namely, those of the 
Caleaire Grossier and the London Clay, the latter indicating 
more temperate climatal conditions. The former is represented 
in England by the Bracklesham series. The areas of these two 
faunas were separated by land forming an isthmus, as each 
formation is bounded by a shore-line and separated from its 
neighbours by freshwater formations ; but this isthmus probably 
shifted its position to the north and south without ever being 
broken through. A vast Eocene river existed, draining a great 
continent stretching westward; the indications of this river 
in Hampshire and Dorsetshire would show it to have been 
there seventeen or eighteen miles wide. —The Lower Tertiaries 
have been’ divided by Prof. Prestwich and the Survey into the 
marine Thanet beds, the fluviatile, estuarine and marine 
Woolwich and Reading Beds, and the marine Oldhaven Beds. 
The mode of occurrence of these was described by the author, 
with especial reference to the section between Herne Bay and 
the Reculvers, from his investigation of which he was led to the 
following conclusions :—The Thanet Sands were probably depo- 
sited by a rough sea outside the estuary of the great Eocene 
river, but within its influence. This area became silted up, rose 
above the surface, and became covered with shingle and sand. 
The Thanet Beds closed with a period of elevation, during which 
the Reading Beds were formed, and this was followed by a 
subsidence during the Woolwich period, which finally ushered 
in the Oldhaven and London Clay deposits. The formation of 
the Oldhaven Beds may be compared with that of the modern 
beach at Shellness ; and during the period of depression the 
beaches would advance steadily over the flat area of Sheppey, 
and the earlier formed ones would sink and become covered up 
by the silt of the great Eocene river, These beaches, forming 
vast aggregations of sand and shingle between the Thanet Beds 
and the London Clay, form integral portions of one or other 
formation, and cannot be recognised as forming a separate 
